Physics and Astronomy Colloquia

Academic Year 2013-2014

Dept. of Physics & Astronomy, Stony Brook University

Colloquium committee: Meigan Aronson (chair), Leonardo Rastelli, Dominik Schneble, Dmitri Tsybychev, Joanna Kiryluk, Alexandre Abanov, and Alan Calder

Coffee & Tea served at 3:45 pm.
Talk begins at 4:15 pm.
Location: Harriman 137 (bottom of square C4 on the campus map)

Fall 2013 colloquia

Date Speaker Title Local Host

Sept. 10 Laszlo Mihaly
Stony Brook Chair's Colloquium

[recorded movie]
-

Sept. 17 Brian de Marco
UIUC Ultracold Disordered Quantum Gases
Disorder is the rule, rather than the exception, in nature. Despite this, we understand little about how disorder affects interacting quantum matter. I will give an overview of our experiments using ultracold atom gases to probe paradigms of interacting disordered quantum particles. We introduce disorder to naturally clean atomic gases cooled to billionths of a degree above absolute zero using focused optical speckle. I will explain how we observe Anderson localization-a spectacular phenomenon in which interference prevents waves from propagating in a disordered medium-of quantum matter in three dimensions. I will also show how we combine speckle with an optical crystal to emulate a completely tunable and precisely characterized disordered quantum solid. In these optical lattice experiments, we realize disordered Hubbard models that we use to answer critical questions regarding how disorder impacts the properties of electronic solids, such as superconductors and metals.
[recorded movie]
Schneble

Sept. 24 Zvi Bern
UCLA Harmony of Scattering Amplitudes: From Quantum Chromodynamics to Supergravity
Recent years have seen enormous advances in our ability to compute elementary-particle scattering amplitudes in quantum field theory, which is the subject of a four month program at the Simons Center. Associated with these advances are the discovery of remarkable new structures obeyed by scattering amplitudes. Examples from particle collider physics and supergravity theories will be given. In collider physics this includes new precision calculations of multi-jet process using quantum chromodynamics. Supergravity theories are shown to be remarkably well behaved in the ultraviolet as a consequence of a newly uncovered connection to gauge theories which shows that gravitons can be viewed as two copies of gluons.
[recorded movie]
Meade

Oct. 1 Neal Weiner
NYU Illuminating Dark Matter
Over the past century, we have become increasingly aware of a mysterious dark component of the universe. While the evidence for one part of it - dark matter - has continued to build, the evidence as to what it is has remained elusive. There are reasons to be optimistic that this era may finally see a discovery of the nature of dark matter. The current generation of experiments promises to make dramatic progress on the idea of "WIMP" dark matter. Additionally, over the past several years, a series of anomalies have pushed our ideas of what dark matter might be, although it remains unclear whether any of these signals are, in fact, arising from dark matter. I will discuss how our thinking has changed, including the ideas of dark forces, and the prospects to make progress on this in the near future.
[recorded movie]
Meade

Oct. 8 Cory Dean
City College of NY One-dimensional contact to a two-dimensional material
The capability to assemble two-dimensional (2D) materials with complementary properties into layered heterogeneous structures presents an exciting new opportunity in materials design. For example, encapsulating graphene with BN yields enhanced transport properties with reduced environmental sensitivity, and provides the capability for complex band structure engineering. Integrating graphene with transition metal dichalcogenides (TMDCs) enables novel tunneling devices and photoactive hybrid materials for flexible electronics. However, the development of device fabrication processes for 2D materials is still in its infancy and several fundamental challenges remain. In particular, successful device engineering depends critically on the ability to make good electrical contact to the encapsulated 2D layers. In this talk I discuss a new device topology where 3D metal electrodes contact encapsulated 2D layers along a 1D interface. We find that this novel contact geometry outperforms conventional surface contacts, in spite of the carrier injection being limited to 1 single 1D atomic chain. Implications for the development of new device geometries and performance will be discussed.
[recorded movie]
Xu Du

Oct. 15 Chang Kee Jung
SBU T2K Experiment: Observation of Electron Neutrino Appearance from a Muon Neutrino Beam
Matter-antimatter asymmetry is one of the most outstanding mysteries of the universe that provided a necessary condition to our own existence. There have been various attempts to solve this mystery including 'Baryogenesis' hypothesis. However, the B-factory experiments during the last decades showed that the observed CP-violation in the quark sector is not big enough for baryogenesis to be a viable solution to the matter-antimatter asymmetry. This leads us to the 'Leptogenesis' hypothesis, in which CP-violation in the lepton section plays a crtical role to create the matter-antimater asymmetry at the onset of the Big Bang. Thus, experimental observation of CP-violation in the lepton sector could prove to be tantamount to one of the most important discoveries in our understanding of the universe.
In 2011, T2K published a result that indicates a non-zero theta_13, the last unknown mixing angle in the lepton sector at that time, at 2.5 sigma level of significance. It was the first evidence of non-zero theta_13 by a single experiemental measurement. Recently, after analyzing two more years of data taken since 2011, the T2K experiment reported "Observation of electron neutrino appearance from a muon neutrino beam" at 7.5 sigma level of significance. While neutrino oscillation has been well-established since the discovery by the Super-Kamiokande experiment in 1998, there have not been an observation of neutrino oscillation in a so-called "appearance mode", and this new T2K observation is the first time an explicit neutrino flavor (electron) appearance is observed from another neutrino flavor (muon). This observation also opens the door to study CPV in neutrinos.
In this talk I will present the details of this discovery and its importance to the future CP-violation measurements in the lepton sector. I will also describe the T2K experiment in some detail, and present other recent results.
[recorded movie]
-

Oct. 22 Scott Ransom
NRAO Detecting Gravitational Waves (and doing other cool physics) with Millisecond Pulsars
The first millisecond pulsar was discovered in 1982. Since that time their use as highly-accurate celestial clocks has improved continually, so that they are now regularly used to measure a variety of general relativistic effects and probe a variety of topics in basic physics, such as the equation of state of matter at supra-nuclear densities. One of their most exciting uses though, is the current North American (NANOGrav) and international (the International Pulsar Timing Array) efforts to directly detect nanohertz frequency gravitational waves, most likely originating from the ensemble of supermassive black hole binaries scattered throughout the universe. In this talk I’ll describe how we are using an ensemble of pulsars to try to make such a measurement, how we could make a detection within the next 5-10 years, and how we get a wide variety of very interesting secondary science from the pulsars in the meantime.
[recorded movie]
Calder/Lattimer

Oct. 29 Pierre Vanhove
IHES Universality Results in Quantum Gravity
Amplitude computations in quantum field theory have seen tremendous progress in the past few years. Fascinating relations between quantum gravity and gauge theory amplitudes have emerged. In this talk, we will display a surprising relation between some amplitudes in pure gravity and quantum electrodynamics (QED). We will show that such relations have deep and far reaching physical consequences. These relations allow us to extract extract classical post-Newtonian corrections and also universal quantum corrections to Newton's laws. These corrections have the remarkable property of depending only on the low-energy degrees of freedom and are independent of the ultraviolet completion. Therefore they are universal quantities for any theory of quantum gravity.
[recorded movie]
Herzog

Nov. 5 Leonid Levitov
MIT Atomic Collapse in Graphene
Since the discovery that electrons in graphene behave as massless Dirac fermions, the single-atom-thick material has become a fertile playground for testing exotic predictions of quantum electrodynamics, such as Klein tunneling and the fractional quantum Hall effect. Now add to that list atomic collapse, the spontaneous formation of electrons and positrons in the electrostatic field of a superheavy atomic nucleus. The atomic collapse was predicted to manifest itself in quasistationary states which have complex-valued energies and which decay rapidly. However, the atoms created artificially in laboratory have nuclear charge only up to Z = 118, which falls short of the predicted threshold for collapse, Interest in this problem has been revived with the advent of graphene, where because of a large fine structure constant the collapse is expected for Z of order unity. In this talk we will discuss the symmetry aspects of atomic collapse, in particular the anomalous breaking of scale invariance. We will also describe recent experiments that use scanning tunneling microscopy (STM) to probe atomic collapse near STM-controlled artificial compound nuclei.
[recorded movie]
Abanov

Nov. 12 Amos Yahil
SBU Life After Astronomy: Applying Basic Principles to Great Advantage in Medical Imaging
Functional medical imaging goes beyond structural characterization to determine the physiological processes in organs of interest. It is expected to become increasingly important as medicine turns more from structural therapy and systemic drugs (surgery, radiation, antibiotics, chemotherapy…) to identifying and treating specific cellular and molecular targets. In this talk I will give a primer to medical imaging and then concentrate on the challenges of weak signal-to-noise and poor resolution in functional imaging. I will show how new data-modeling techniques can greatly improve imaging. In particular, I will present a new method of image reconstruction called xSPECT that I developed with Siemens for Single Photon Emission Computed Tomography, which significantly enhances resolution. (See below a conventional SPECT image on the left compared with an xSPECT image on the right.) xSPECT is also quantitative, enabling objective monitoring of patient progress.

[recorded movie]
Calder

Nov. 19 Fred Goldhaber
SBU Niels Bohr and the Third Quantum Revolution -- Centennial of the Rutherford-Bohr Atom
In the history of science few developments can rival the discovery of quantum mechanics, with its series of abrupt leaps in unexpected directions stretching over a quarter century. The result was a new world, even more strange than any previously imagined subterranean (or in this case submicroscopic) kingdom. Niels Bohr made the third of these leaps (following Planck and Einstein) when he realized that still-new quantum ideas were essential to account for atomic structure: Rutherford had deduced, using entirely classical-physics principles, that the positive charge in an atom is contained in a very small kernel or nucleus. This made the atom an analogue to the solar system.
Classical physics implied that negatively charged electrons losing energy to electromagnetic radiation would ``dive in'' to the nucleus in a very short time. The chemistry of such tiny atoms would be trivial, and the sizes of solids made from these atoms would be much too small. Bohr initially got out of this dilemma by using what he later called the Correspondence Principle to deduce that the angular momentum of an electron orbiting about the nucleus should be quantized in integer multiples of the reduced quantum constant ℏ= h/2π. Solving for the energy of such an orbit in equilibrium immediately produces the famous Balmer formula for the frequencies of visible light radiated from hydrogen as an electron jumps from any particular orbit to another of lower energy.
There remained mysteries requiring explanation or at least exploration, including two to be discussed here: 1. Rutherford used classical mechanics to compute the trajectory and hence the scattering angle of an alpha particle impinging on a small positively charged target. How could this be consistent with Bohr's quantization of particle orbits about the nucleus? 2. Bohr excluded for his integer multiples of ℏ the value 0. How can one justify this exclusion, necessary to bar tiny atoms of the type mentioned earlier?
[recorded movie]
-

Nov. 26 Young-Kee Kim
U. Chicago U.S. Particle Physics: Where are we going?
Experiments in particle physics have led to a consistent theory of the origins of our world - but only up to a certain point. This theory has within it the seeds of its own demise. Moreover, particle physics - physics of the very small - is intimately connected to cosmology – physics of the very big. Cosmological observations also point to the need for a new physical theory. In this colloquium, I will trace out the path from where we are now to where we need to go in order to take the next steps towards solving these mysteries. This journey requires global-scale projects. I will describe how the international particle-physics community is developing plans for creating such facilities. I will also discuss some of the obstacles for the U.S. to compete for these big science projects. A new framework may be needed to overcome these obstacles.
[recorded movie]
Tsybychev

Dec. 3 Angela Kelly
SBU Active Learning and Instructional Reforms in the Physics Classroom
The call for improvement in STEM education in the United States has reached epic proportions in recent years. In their widely publicized report, Rising Above the Gathering Storm, the National Academies has called for vast changes in STEM education. Among the most pressing issues that the STEM education community has been trying to address are students’ inadequate preparation for college-level STEM coursework, the widening of the achievement gap among underrepresented groups, and the low numbers of students who major in science and mathematics.
The American Physical Society has stated that the best way to remediate these issues is to improve introductory physics teaching and learning. Reformed pedagogical practices in introductory STEM coursework have been shown to improve students’ classroom experiences and persistence in STEM majors and careers. This seminar will highlight recent departmental reforms at Stony Brook, as well as proposed research-based instructional models that may be replicated at the Stony Brook campus. These models will include MIT’s Technology-Enabled Active Learning (TEAL) project, Studio Physics at North Carolina State University and Central Florida University, and Eric Mazur’s active learning techniques at Harvard University. Data will be shared to illustrate the impacts of these transformative practices.
[recorded movie]
-

Date	Speaker	Title	Local Host
Sept. 10	Laszlo Mihaly Stony Brook	Chair's Colloquium [recorded movie]	-
Sept. 17	Brian de Marco UIUC	Ultracold Disordered Quantum Gases Disorder is the rule, rather than the exception, in nature. Despite this, we understand little about how disorder affects interacting quantum matter. I will give an overview of our experiments using ultracold atom gases to probe paradigms of interacting disordered quantum particles. We introduce disorder to naturally clean atomic gases cooled to billionths of a degree above absolute zero using focused optical speckle. I will explain how we observe Anderson localization-a spectacular phenomenon in which interference prevents waves from propagating in a disordered medium-of quantum matter in three dimensions. I will also show how we combine speckle with an optical crystal to emulate a completely tunable and precisely characterized disordered quantum solid. In these optical lattice experiments, we realize disordered Hubbard models that we use to answer critical questions regarding how disorder impacts the properties of electronic solids, such as superconductors and metals. [recorded movie]	Schneble
Sept. 24	Zvi Bern UCLA	Harmony of Scattering Amplitudes: From Quantum Chromodynamics to Supergravity Recent years have seen enormous advances in our ability to compute elementary-particle scattering amplitudes in quantum field theory, which is the subject of a four month program at the Simons Center. Associated with these advances are the discovery of remarkable new structures obeyed by scattering amplitudes. Examples from particle collider physics and supergravity theories will be given. In collider physics this includes new precision calculations of multi-jet process using quantum chromodynamics. Supergravity theories are shown to be remarkably well behaved in the ultraviolet as a consequence of a newly uncovered connection to gauge theories which shows that gravitons can be viewed as two copies of gluons. [recorded movie]	Meade
Oct. 1	Neal Weiner NYU	Illuminating Dark Matter Over the past century, we have become increasingly aware of a mysterious dark component of the universe. While the evidence for one part of it - dark matter - has continued to build, the evidence as to what it is has remained elusive. There are reasons to be optimistic that this era may finally see a discovery of the nature of dark matter. The current generation of experiments promises to make dramatic progress on the idea of "WIMP" dark matter. Additionally, over the past several years, a series of anomalies have pushed our ideas of what dark matter might be, although it remains unclear whether any of these signals are, in fact, arising from dark matter. I will discuss how our thinking has changed, including the ideas of dark forces, and the prospects to make progress on this in the near future. [recorded movie]	Meade
Oct. 8	Cory Dean City College of NY	One-dimensional contact to a two-dimensional material The capability to assemble two-dimensional (2D) materials with complementary properties into layered heterogeneous structures presents an exciting new opportunity in materials design. For example, encapsulating graphene with BN yields enhanced transport properties with reduced environmental sensitivity, and provides the capability for complex band structure engineering. Integrating graphene with transition metal dichalcogenides (TMDCs) enables novel tunneling devices and photoactive hybrid materials for flexible electronics. However, the development of device fabrication processes for 2D materials is still in its infancy and several fundamental challenges remain. In particular, successful device engineering depends critically on the ability to make good electrical contact to the encapsulated 2D layers. In this talk I discuss a new device topology where 3D metal electrodes contact encapsulated 2D layers along a 1D interface. We find that this novel contact geometry outperforms conventional surface contacts, in spite of the carrier injection being limited to 1 single 1D atomic chain. Implications for the development of new device geometries and performance will be discussed. [recorded movie]	Xu Du
Oct. 15	Chang Kee Jung SBU	T2K Experiment: Observation of Electron Neutrino Appearance from a Muon Neutrino Beam Matter-antimatter asymmetry is one of the most outstanding mysteries of the universe that provided a necessary condition to our own existence. There have been various attempts to solve this mystery including 'Baryogenesis' hypothesis. However, the B-factory experiments during the last decades showed that the observed CP-violation in the quark sector is not big enough for baryogenesis to be a viable solution to the matter-antimatter asymmetry. This leads us to the 'Leptogenesis' hypothesis, in which CP-violation in the lepton section plays a crtical role to create the matter-antimater asymmetry at the onset of the Big Bang. Thus, experimental observation of CP-violation in the lepton sector could prove to be tantamount to one of the most important discoveries in our understanding of the universe. In 2011, T2K published a result that indicates a non-zero theta_13, the last unknown mixing angle in the lepton sector at that time, at 2.5 sigma level of significance. It was the first evidence of non-zero theta_13 by a single experiemental measurement. Recently, after analyzing two more years of data taken since 2011, the T2K experiment reported "Observation of electron neutrino appearance from a muon neutrino beam" at 7.5 sigma level of significance. While neutrino oscillation has been well-established since the discovery by the Super-Kamiokande experiment in 1998, there have not been an observation of neutrino oscillation in a so-called "appearance mode", and this new T2K observation is the first time an explicit neutrino flavor (electron) appearance is observed from another neutrino flavor (muon). This observation also opens the door to study CPV in neutrinos. In this talk I will present the details of this discovery and its importance to the future CP-violation measurements in the lepton sector. I will also describe the T2K experiment in some detail, and present other recent results. [recorded movie]	-
Oct. 22	Scott Ransom NRAO	Detecting Gravitational Waves (and doing other cool physics) with Millisecond Pulsars The first millisecond pulsar was discovered in 1982. Since that time their use as highly-accurate celestial clocks has improved continually, so that they are now regularly used to measure a variety of general relativistic effects and probe a variety of topics in basic physics, such as the equation of state of matter at supra-nuclear densities. One of their most exciting uses though, is the current North American (NANOGrav) and international (the International Pulsar Timing Array) efforts to directly detect nanohertz frequency gravitational waves, most likely originating from the ensemble of supermassive black hole binaries scattered throughout the universe. In this talk I’ll describe how we are using an ensemble of pulsars to try to make such a measurement, how we could make a detection within the next 5-10 years, and how we get a wide variety of very interesting secondary science from the pulsars in the meantime. [recorded movie]	Calder/Lattimer
Oct. 29	Pierre Vanhove IHES	Universality Results in Quantum Gravity Amplitude computations in quantum field theory have seen tremendous progress in the past few years. Fascinating relations between quantum gravity and gauge theory amplitudes have emerged. In this talk, we will display a surprising relation between some amplitudes in pure gravity and quantum electrodynamics (QED). We will show that such relations have deep and far reaching physical consequences. These relations allow us to extract extract classical post-Newtonian corrections and also universal quantum corrections to Newton's laws. These corrections have the remarkable property of depending only on the low-energy degrees of freedom and are independent of the ultraviolet completion. Therefore they are universal quantities for any theory of quantum gravity. [recorded movie]	Herzog
Nov. 5	Leonid Levitov MIT	Atomic Collapse in Graphene Since the discovery that electrons in graphene behave as massless Dirac fermions, the single-atom-thick material has become a fertile playground for testing exotic predictions of quantum electrodynamics, such as Klein tunneling and the fractional quantum Hall effect. Now add to that list atomic collapse, the spontaneous formation of electrons and positrons in the electrostatic field of a superheavy atomic nucleus. The atomic collapse was predicted to manifest itself in quasistationary states which have complex-valued energies and which decay rapidly. However, the atoms created artificially in laboratory have nuclear charge only up to Z = 118, which falls short of the predicted threshold for collapse, Interest in this problem has been revived with the advent of graphene, where because of a large fine structure constant the collapse is expected for Z of order unity. In this talk we will discuss the symmetry aspects of atomic collapse, in particular the anomalous breaking of scale invariance. We will also describe recent experiments that use scanning tunneling microscopy (STM) to probe atomic collapse near STM-controlled artificial compound nuclei. [recorded movie]	Abanov
Nov. 12	Amos Yahil SBU	Life After Astronomy: Applying Basic Principles to Great Advantage in Medical Imaging Functional medical imaging goes beyond structural characterization to determine the physiological processes in organs of interest. It is expected to become increasingly important as medicine turns more from structural therapy and systemic drugs (surgery, radiation, antibiotics, chemotherapy…) to identifying and treating specific cellular and molecular targets. In this talk I will give a primer to medical imaging and then concentrate on the challenges of weak signal-to-noise and poor resolution in functional imaging. I will show how new data-modeling techniques can greatly improve imaging. In particular, I will present a new method of image reconstruction called xSPECT that I developed with Siemens for Single Photon Emission Computed Tomography, which significantly enhances resolution. (See below a conventional SPECT image on the left compared with an xSPECT image on the right.) xSPECT is also quantitative, enabling objective monitoring of patient progress. [recorded movie]	Calder
Nov. 19	Fred Goldhaber SBU	Niels Bohr and the Third Quantum Revolution -- Centennial of the Rutherford-Bohr Atom In the history of science few developments can rival the discovery of quantum mechanics, with its series of abrupt leaps in unexpected directions stretching over a quarter century. The result was a new world, even more strange than any previously imagined subterranean (or in this case submicroscopic) kingdom. Niels Bohr made the third of these leaps (following Planck and Einstein) when he realized that still-new quantum ideas were essential to account for atomic structure: Rutherford had deduced, using entirely classical-physics principles, that the positive charge in an atom is contained in a very small kernel or nucleus. This made the atom an analogue to the solar system. Classical physics implied that negatively charged electrons losing energy to electromagnetic radiation would ``dive in'' to the nucleus in a very short time. The chemistry of such tiny atoms would be trivial, and the sizes of solids made from these atoms would be much too small. Bohr initially got out of this dilemma by using what he later called the Correspondence Principle to deduce that the angular momentum of an electron orbiting about the nucleus should be quantized in integer multiples of the reduced quantum constant ℏ= h/2π. Solving for the energy of such an orbit in equilibrium immediately produces the famous Balmer formula for the frequencies of visible light radiated from hydrogen as an electron jumps from any particular orbit to another of lower energy. There remained mysteries requiring explanation or at least exploration, including two to be discussed here: 1. Rutherford used classical mechanics to compute the trajectory and hence the scattering angle of an alpha particle impinging on a small positively charged target. How could this be consistent with Bohr's quantization of particle orbits about the nucleus? 2. Bohr excluded for his integer multiples of ℏ the value 0. How can one justify this exclusion, necessary to bar tiny atoms of the type mentioned earlier? [recorded movie]	-
Nov. 26	Young-Kee Kim U. Chicago	U.S. Particle Physics: Where are we going? Experiments in particle physics have led to a consistent theory of the origins of our world - but only up to a certain point. This theory has within it the seeds of its own demise. Moreover, particle physics - physics of the very small - is intimately connected to cosmology – physics of the very big. Cosmological observations also point to the need for a new physical theory. In this colloquium, I will trace out the path from where we are now to where we need to go in order to take the next steps towards solving these mysteries. This journey requires global-scale projects. I will describe how the international particle-physics community is developing plans for creating such facilities. I will also discuss some of the obstacles for the U.S. to compete for these big science projects. A new framework may be needed to overcome these obstacles. [recorded movie]	Tsybychev
Dec. 3	Angela Kelly SBU	Active Learning and Instructional Reforms in the Physics Classroom The call for improvement in STEM education in the United States has reached epic proportions in recent years. In their widely publicized report, Rising Above the Gathering Storm, the National Academies has called for vast changes in STEM education. Among the most pressing issues that the STEM education community has been trying to address are students’ inadequate preparation for college-level STEM coursework, the widening of the achievement gap among underrepresented groups, and the low numbers of students who major in science and mathematics. The American Physical Society has stated that the best way to remediate these issues is to improve introductory physics teaching and learning. Reformed pedagogical practices in introductory STEM coursework have been shown to improve students’ classroom experiences and persistence in STEM majors and careers. This seminar will highlight recent departmental reforms at Stony Brook, as well as proposed research-based instructional models that may be replicated at the Stony Brook campus. These models will include MIT’s Technology-Enabled Active Learning (TEAL) project, Studio Physics at North Carolina State University and Central Florida University, and Eric Mazur’s active learning techniques at Harvard University. Data will be shared to illustrate the impacts of these transformative practices. [recorded movie]	-

Spring 2014 colloquia

Date Speaker Title Local Host

Jan. 28 Steffen Wirth
MPI CPfS Dresden An STM view on strongly correlated electron systems: From metals to insulators
Hybridization is a fundamental concept in strongly correlated electron physics. In heavy fermion metals, it may result in the generation of low-energy scales that can give rise to quantum criticality and unconventional superconductivity. An introduction to the Kondo interaction and hybridization effects will be given, with focus on the heavy fermion system YbRh₂Si₂ and the intermediate valence insulator SmB₆. Similarities and differences will be highlighted. The material YbRh₂Si₂ is of specific topical interest due to a quantum critical point which appears to result not only from an antiferromagnetic instability but also from a Kondo break-down of the heavy quasiparticles [1]. We present Scanning Tunneling Microscopy (STM) and Spectroscopy (STS) studies at low temperature [2]. The tunneling conductance clearly reflects the local Kondo interaction as well as the crystal field excitations. In addition, the evolution of the Kondo lattice at low temperatures is investigated: While the Kondo lattice starts forming already at the single-ion Kondo temperature it dominates the material properties only at much lower temperatures. These findings by STS are augmented by additional measurements [3,4]. Hybridization also plays a decisive role in the low temperature properties of the intermediate valence system SmB₆. The hybridization gap and intermultiplet transitions are clearly observed by STS. The temperature evolution of these spectra again points toward the Kondo effect being at play. STS conducted on non-reconstructed surfaces gave results in excellent agreement with expectations for a Fano resonance. The impact of the surface properties.specifically of surface reconstructions.on the STS data is discussed, also in relation to the recent proposal of a topologically protected surface state in SmB₆ [5].
In collaboration with S. Ernst, Z. Fisk, C. Geibel, Tae-Hwan Jang, S. Kirchner, C. Krellner, S. Roessler, S. Seiro, F. Steglich, L. H. Tjeng and G. Zwicknagl.

S. Friedemann et al., Proc. Natl. Acad. Sci. USA 107 (2010) 14547

S. Ernst et al., Nature 474 (2011) 362

H. Pfau et al., Phys. Rev. Lett. 110 (2013) 256403

H. R. Naren et al., New J. Phys., 15 (2013) 093032

M. Dzero et al., Phys. Rev. Lett. 104 (2010) 106408

[recorded movie]
Aronson

Feb. 4 Jin Koda
SBU Evolution of Molecular Gas and Star Formation in Galaxies
I will discuss the large-scale distribution, evolution, and dynamics of giant molecular clouds (GMCs) in galaxies. The talk is mostly based on the results on M51, but I will also summarize recent results from the CARMA and Nobeyama Nearby-galaxies (CANON) CO 1-0 survey and the CO observations of the Milky Way. The standard, albeit simplistic, picture of ISM phases posits that GMCs are assembled in the spiral arm shocks from diffuse interarm HI gas and then photo-dissociated back into the atomic phase by OB star formation within the spiral arms. However, we are finding many GMCs both on spiral arms and in interarm regions, indicating their long lifetime comparable to galactic rotation timescale. The associations of GMCs (so-called GMAs) are found only on spiral arms, and thus, they are likely unbound, short-lived structures, being broken up across spiral arms. A molecular gas fraction stays high even in interarm regions. Therefore, the GMA destruction is not likely caused by stellar feedback such as strong UV radiation or supernovae, since they would destroy molecules as well as GMAs and GMCs. Instead, I will introduce a picture of dynamically-driven evolution -- strong shear motions in spiral arms cause the GMA destruction and trigger GMC evolution. On small scales, dense gas cores are expected to develop in GMCs through spiral arms, leading to star formation. I will also discuss evidence for such growth in nearby spiral galaxies and in the Milky Way.
[recorded movie]
-

Feb. 11 Dmitri Tsybychev
SBU Studies of Electroweak Symmetry Breaking at the LHC.
The last piece of the Standard Model puzzle, the Higgs boson, is now found and intensive studies are now underway to prove that it posses properties predicted by the Standard Model. Understanding of electroweak symmetry breaking mechanism is one of the highest priority problems facing the field of high-energy physics and most importantly whether such breaking occurs solely through the weak interactions. ATLAS and CMS experiments at Large Hadron Collider at CERN pursuing vigorous physics program to confirm the Higgs mechanism or find possible hints of physics beyond the Standard Model. I will discuss some of such studies performed at ATLAS experiment.
[recorded movie]
-

Feb. 18 Dam Son
Chicago Hydrodynamics and quantum anomalies
Hydrodynamics is the theory describing collective behaviors of fluids and gases. It has a very long history and is usually considered to belong to the realm of classical physics. In recent years, it has been found that, in many cases, hydrodynamics can manifest a purely quantum effect --- anomalies. We will see how this new appreciation of the interplay between quantum and classical physics has emerged, unexpectedly, through the idea of gauge/gravity duality, which originates in modern string theory. I will briefly mention the possible relevance of the new findings to the physics of the quark gluon plasma.
Note: Special SCGP-Physics colloquium to be held in the Simons Center.
Tsybychev

Feb. 25 Rocky Kolb
Chicago The Decade of the WIMP
The bulk of the matter in the present universe is dark. The most attractive possibility for the nature of the dark matter is a new species of elementary particle known as a WIMP (a Weakly Interacting Massive Particle). After a discussion of how a WIMP might fit into models of particle physics, I will review the current situation with respect to direct detection, indirect detection, and collider production of WIMPs. Rapid advances in the field should enable us to answer by the end of the decade whether our universe is dominated by WIMPs.
[recorded movie]
Tsybych

Mar. 4 Special SCGP Event
Frank Wilczek: “Expanding the Doors of Perception”
-

Mar. 11 Frank Timmes
Arizona State Hunting the Progenitors of Supernovae Type Ia
Supernovae Type Ia play a premier role in stellar evolution, galaxy evolution and cosmology. Yet, the identification of what is exploding remains unknown - this is the outstanding mystery in the field. I will review the current situation and explore some recent developments that aim to reveal the unknown progenitor system(s) through observable signatures in their spectra, light curves, and nucleosynthesis. Advances (plus a little serendipity) over the next decade should enable us to decipher the progenitors of Supernovae Type Ia.
[recorded movie]
Calder

Mar. 18 no colloquium—Spring Break

Mar. 25 Wick Haxton
LBNL Solar Neutrinos and Solar System Formation
A problem in the standard solar model has arisen recently -- a disagreement between tests of surface metalicity (photospheric absorption lines) and interior metalicity (helioseismology). The discrepancy has an interesting connection to certain solar neutrino experiments (Borexino and especially SNO+), which may have the reach necessary to settle this question by directly measuring the amount of C and N in the Sun's core. Such a measurement is important, as the discrepancy may be connected to a very interesting stage of solar system formation -- the last few million years of the nebular disk, when the process of planetary formation scrubbed between 50 and 100 earth masses of metal from the remaining nebular gas. The implications range from planet hunting to decoding the Sun’s structure. I will describe recent observations of solar twins that have made speculations of a planetary connection particularly interesting.
[slides]
[recorded movie]
Kiryluk

Apr. 1 Gabriel Aeppli
LCN The next life of silicon
The 20th century has been distinguished by the silicon-based information revolution, where bits are encoded as charges which are manipulated and stored via field effect transistors. The continued exponential growth of information technology based on straightforward extrapolations of this paradigm is not guaranteed, and there has therefore been a search for both alternative paradigms and materials. The new paradigms entail exploitation of spin and orbital degrees of freedom, including related quantum phenomena. While “exotic” materials have been successfully used to demonstrate some of the associated physics, we show here that silicon may be an excellent host for the new effects. In particular, laser cooling and electromagnetic traps have led to a revolution in atomic physics, yielding dramatic discoveries ranging from Bose-Einstein condensation to quantum control of single atoms. Because it is a semiconductor of extraordinary cleanliness which can be acquired at reasonable cost, silicon can also be thought of as an atom trap. We describe here the beginnings of the science of silicon as atom trap, where the trapped atoms are the donor impurities. Key tools, enabling the visualization and manipulation of the impurity quantum states, are free electron lasers and scanning tunneling microscopes.

Greenland et al., Nature (2010)

Vinh et al., PRX (2013)

Morley et al, Nature Materials (2010)

Morley et al, Nature Materials (2013)

Schofield et al., Nature Comm. (2013)

[recorded movie]
Aronson

Apr. 8 Lars Bildsten
UCSB Hearing the Stars: New Insights into Stellar Interiors from Asteroseismology
Long-term and sensitive space-based photometry from the Kepler and CoRoT satellites has allowed us to finally 'hear' the stars. These remarkable data have yielded accurate measurements of masses, radii and distances for more than 10,000 stars across the Milky Way. More profoundly, these observations are revealing the interior conditions of the star, clearly differentiating those that are undergoing helium burning in their cores to those that are only burning hydrogen in a shell. Moreover, interior rotation rates for thousands of post-main sequence stars will soon be known, probing the uncertain physics of angular momentum transport that is important to the progenitors of core collapse supernova.
[recorded movie]
Calder

Apr. 15 Brad Marston
Brown The Quantum and Fluid Mechanics of Global Warming
Quantum mechanics plays a crucial, albeit often overlooked, role in our understanding of the Earth's climate. In this talk three well known aspects of quantum mechanics are invoked to present a simple physical picture of what will happen as the concentrations of greenhouse gases such as carbon dioxide continue to increase. Historical and paleoclimatic records are interpreted with some basic astronomy, fluid mechanics, and the use of fundamental laws of physics such as the conservation of angular momentum. Live simulations will illustrate the basic physical principles governing large scale atmospheric circulation. I conclude by discussing some possible ways that physics might be able to contribute to a deeper understanding of climate change.
See Physics Trends, "Looking for new problems to solve? Consider the climate" at http://physics.aps.org/articles/v4/20

[recorded movie]
Abanov

Apr. 22 Jennifer Hoffman
Harvard Topological Materials at the Nanoscale
Once or twice per decade, the discovery of a new class of electronic materials takes the world by storm, generating thousands of scientific publications per year, and broad hopes for practical applications. In this category are the so-called “topological materials” – typically insulators hosting topologically protected metallic surface states whose strongly coupled spin and momentum degrees of freedom have prompted numerous proposals for nanoscale devices. After an introduction to topological materials, I will describe efforts in my laboratory to measure their properties via low temperature scanning tunneling microscopy. In the topological semimetal antimony (Sb), we study the effects of single-atom defects, we quantify parameters relevant to spintronics applications, and we establish new techniques for nanoscale band structure measurements. We further apply these techniques to SmB6, whose anomalous electronic properties have remained mysterious for almost 50 years, but may finally be explained as arising from a topological Kondo insulator phase.
[recorded movie]
Aronson

Apr. 29 Horacio Casini
Centro Atómico Bariloche Quantum entanglement and relativity: From Bekenstein’s bound to c-theorems
Quantum entanglement in extended systems has been the subject of much interest in recent years, with applications ranging from condensed matter physics to holography and black holes. In this talk I will review several aspects of entanglement entropy in relativistic theories. The combination of causality and Lorentz symmetry imposes an “area law” to entanglement entropy which resembles the formula of the entropy of black holes. Finite deviations from the area law contain important information on the physics of the continuum quantum field theory. I will show how general properties of quantum entropy applied to these finite terms give a proof of Bekenstein’s universal bound on entropy by the product of energy and size. I will also discuss how the entropy contained in vacuum fluctuations give a meassure of the irreversibility of the renormalization group in low-dimensional quantum field theories.
[recorded movie]
Herzog

May 6 graduate director
Graduate Awards Colloquium

[recorded movie]
-

Date	Speaker	Title	Local Host
Jan. 28	Steffen Wirth MPI CPfS Dresden	An STM view on strongly correlated electron systems: From metals to insulators Hybridization is a fundamental concept in strongly correlated electron physics. In heavy fermion metals, it may result in the generation of low-energy scales that can give rise to quantum criticality and unconventional superconductivity. An introduction to the Kondo interaction and hybridization effects will be given, with focus on the heavy fermion system YbRh₂Si₂ and the intermediate valence insulator SmB₆. Similarities and differences will be highlighted. The material YbRh₂Si₂ is of specific topical interest due to a quantum critical point which appears to result not only from an antiferromagnetic instability but also from a Kondo break-down of the heavy quasiparticles [1]. We present Scanning Tunneling Microscopy (STM) and Spectroscopy (STS) studies at low temperature [2]. The tunneling conductance clearly reflects the local Kondo interaction as well as the crystal field excitations. In addition, the evolution of the Kondo lattice at low temperatures is investigated: While the Kondo lattice starts forming already at the single-ion Kondo temperature it dominates the material properties only at much lower temperatures. These findings by STS are augmented by additional measurements [3,4]. Hybridization also plays a decisive role in the low temperature properties of the intermediate valence system SmB₆. The hybridization gap and intermultiplet transitions are clearly observed by STS. The temperature evolution of these spectra again points toward the Kondo effect being at play. STS conducted on non-reconstructed surfaces gave results in excellent agreement with expectations for a Fano resonance. The impact of the surface properties.specifically of surface reconstructions.on the STS data is discussed, also in relation to the recent proposal of a topologically protected surface state in SmB₆ [5]. In collaboration with S. Ernst, Z. Fisk, C. Geibel, Tae-Hwan Jang, S. Kirchner, C. Krellner, S. Roessler, S. Seiro, F. Steglich, L. H. Tjeng and G. Zwicknagl. S. Friedemann et al., Proc. Natl. Acad. Sci. USA 107 (2010) 14547 S. Ernst et al., Nature 474 (2011) 362 H. Pfau et al., Phys. Rev. Lett. 110 (2013) 256403 H. R. Naren et al., New J. Phys., 15 (2013) 093032 M. Dzero et al., Phys. Rev. Lett. 104 (2010) 106408 [recorded movie]	Aronson
Feb. 4	Jin Koda SBU	Evolution of Molecular Gas and Star Formation in Galaxies I will discuss the large-scale distribution, evolution, and dynamics of giant molecular clouds (GMCs) in galaxies. The talk is mostly based on the results on M51, but I will also summarize recent results from the CARMA and Nobeyama Nearby-galaxies (CANON) CO 1-0 survey and the CO observations of the Milky Way. The standard, albeit simplistic, picture of ISM phases posits that GMCs are assembled in the spiral arm shocks from diffuse interarm HI gas and then photo-dissociated back into the atomic phase by OB star formation within the spiral arms. However, we are finding many GMCs both on spiral arms and in interarm regions, indicating their long lifetime comparable to galactic rotation timescale. The associations of GMCs (so-called GMAs) are found only on spiral arms, and thus, they are likely unbound, short-lived structures, being broken up across spiral arms. A molecular gas fraction stays high even in interarm regions. Therefore, the GMA destruction is not likely caused by stellar feedback such as strong UV radiation or supernovae, since they would destroy molecules as well as GMAs and GMCs. Instead, I will introduce a picture of dynamically-driven evolution -- strong shear motions in spiral arms cause the GMA destruction and trigger GMC evolution. On small scales, dense gas cores are expected to develop in GMCs through spiral arms, leading to star formation. I will also discuss evidence for such growth in nearby spiral galaxies and in the Milky Way. [recorded movie]	-
Feb. 11	Dmitri Tsybychev SBU	Studies of Electroweak Symmetry Breaking at the LHC. The last piece of the Standard Model puzzle, the Higgs boson, is now found and intensive studies are now underway to prove that it posses properties predicted by the Standard Model. Understanding of electroweak symmetry breaking mechanism is one of the highest priority problems facing the field of high-energy physics and most importantly whether such breaking occurs solely through the weak interactions. ATLAS and CMS experiments at Large Hadron Collider at CERN pursuing vigorous physics program to confirm the Higgs mechanism or find possible hints of physics beyond the Standard Model. I will discuss some of such studies performed at ATLAS experiment. [recorded movie]	-
Feb. 18	Dam Son Chicago	Hydrodynamics and quantum anomalies Hydrodynamics is the theory describing collective behaviors of fluids and gases. It has a very long history and is usually considered to belong to the realm of classical physics. In recent years, it has been found that, in many cases, hydrodynamics can manifest a purely quantum effect --- anomalies. We will see how this new appreciation of the interplay between quantum and classical physics has emerged, unexpectedly, through the idea of gauge/gravity duality, which originates in modern string theory. I will briefly mention the possible relevance of the new findings to the physics of the quark gluon plasma. Note: Special SCGP-Physics colloquium to be held in the Simons Center.	Tsybychev
Feb. 25	Rocky Kolb Chicago	The Decade of the WIMP The bulk of the matter in the present universe is dark. The most attractive possibility for the nature of the dark matter is a new species of elementary particle known as a WIMP (a Weakly Interacting Massive Particle). After a discussion of how a WIMP might fit into models of particle physics, I will review the current situation with respect to direct detection, indirect detection, and collider production of WIMPs. Rapid advances in the field should enable us to answer by the end of the decade whether our universe is dominated by WIMPs. [recorded movie]	Tsybych
Mar. 4	Special SCGP Event	Frank Wilczek: “Expanding the Doors of Perception”	-
Mar. 11	Frank Timmes Arizona State	Hunting the Progenitors of Supernovae Type Ia Supernovae Type Ia play a premier role in stellar evolution, galaxy evolution and cosmology. Yet, the identification of what is exploding remains unknown - this is the outstanding mystery in the field. I will review the current situation and explore some recent developments that aim to reveal the unknown progenitor system(s) through observable signatures in their spectra, light curves, and nucleosynthesis. Advances (plus a little serendipity) over the next decade should enable us to decipher the progenitors of Supernovae Type Ia. [recorded movie]	Calder
Mar. 18	no colloquium—Spring Break
Mar. 25	Wick Haxton LBNL	Solar Neutrinos and Solar System Formation A problem in the standard solar model has arisen recently -- a disagreement between tests of surface metalicity (photospheric absorption lines) and interior metalicity (helioseismology). The discrepancy has an interesting connection to certain solar neutrino experiments (Borexino and especially SNO+), which may have the reach necessary to settle this question by directly measuring the amount of C and N in the Sun's core. Such a measurement is important, as the discrepancy may be connected to a very interesting stage of solar system formation -- the last few million years of the nebular disk, when the process of planetary formation scrubbed between 50 and 100 earth masses of metal from the remaining nebular gas. The implications range from planet hunting to decoding the Sun’s structure. I will describe recent observations of solar twins that have made speculations of a planetary connection particularly interesting. [slides] [recorded movie]	Kiryluk
Apr. 1	Gabriel Aeppli LCN	The next life of silicon The 20th century has been distinguished by the silicon-based information revolution, where bits are encoded as charges which are manipulated and stored via field effect transistors. The continued exponential growth of information technology based on straightforward extrapolations of this paradigm is not guaranteed, and there has therefore been a search for both alternative paradigms and materials. The new paradigms entail exploitation of spin and orbital degrees of freedom, including related quantum phenomena. While “exotic” materials have been successfully used to demonstrate some of the associated physics, we show here that silicon may be an excellent host for the new effects. In particular, laser cooling and electromagnetic traps have led to a revolution in atomic physics, yielding dramatic discoveries ranging from Bose-Einstein condensation to quantum control of single atoms. Because it is a semiconductor of extraordinary cleanliness which can be acquired at reasonable cost, silicon can also be thought of as an atom trap. We describe here the beginnings of the science of silicon as atom trap, where the trapped atoms are the donor impurities. Key tools, enabling the visualization and manipulation of the impurity quantum states, are free electron lasers and scanning tunneling microscopes. Greenland et al., Nature (2010) Vinh et al., PRX (2013) Morley et al, Nature Materials (2010) Morley et al, Nature Materials (2013) Schofield et al., Nature Comm. (2013) [recorded movie]	Aronson
Apr. 8	Lars Bildsten UCSB	Hearing the Stars: New Insights into Stellar Interiors from Asteroseismology Long-term and sensitive space-based photometry from the Kepler and CoRoT satellites has allowed us to finally 'hear' the stars. These remarkable data have yielded accurate measurements of masses, radii and distances for more than 10,000 stars across the Milky Way. More profoundly, these observations are revealing the interior conditions of the star, clearly differentiating those that are undergoing helium burning in their cores to those that are only burning hydrogen in a shell. Moreover, interior rotation rates for thousands of post-main sequence stars will soon be known, probing the uncertain physics of angular momentum transport that is important to the progenitors of core collapse supernova. [recorded movie]	Calder
Apr. 15	Brad Marston Brown	The Quantum and Fluid Mechanics of Global Warming Quantum mechanics plays a crucial, albeit often overlooked, role in our understanding of the Earth's climate. In this talk three well known aspects of quantum mechanics are invoked to present a simple physical picture of what will happen as the concentrations of greenhouse gases such as carbon dioxide continue to increase. Historical and paleoclimatic records are interpreted with some basic astronomy, fluid mechanics, and the use of fundamental laws of physics such as the conservation of angular momentum. Live simulations will illustrate the basic physical principles governing large scale atmospheric circulation. I conclude by discussing some possible ways that physics might be able to contribute to a deeper understanding of climate change. See Physics Trends, "Looking for new problems to solve? Consider the climate" at http://physics.aps.org/articles/v4/20 [recorded movie]	Abanov
Apr. 22	Jennifer Hoffman Harvard	Topological Materials at the Nanoscale Once or twice per decade, the discovery of a new class of electronic materials takes the world by storm, generating thousands of scientific publications per year, and broad hopes for practical applications. In this category are the so-called “topological materials” – typically insulators hosting topologically protected metallic surface states whose strongly coupled spin and momentum degrees of freedom have prompted numerous proposals for nanoscale devices. After an introduction to topological materials, I will describe efforts in my laboratory to measure their properties via low temperature scanning tunneling microscopy. In the topological semimetal antimony (Sb), we study the effects of single-atom defects, we quantify parameters relevant to spintronics applications, and we establish new techniques for nanoscale band structure measurements. We further apply these techniques to SmB6, whose anomalous electronic properties have remained mysterious for almost 50 years, but may finally be explained as arising from a topological Kondo insulator phase. [recorded movie]	Aronson
Apr. 29	Horacio Casini Centro Atómico Bariloche	Quantum entanglement and relativity: From Bekenstein’s bound to c-theorems Quantum entanglement in extended systems has been the subject of much interest in recent years, with applications ranging from condensed matter physics to holography and black holes. In this talk I will review several aspects of entanglement entropy in relativistic theories. The combination of causality and Lorentz symmetry imposes an “area law” to entanglement entropy which resembles the formula of the entropy of black holes. Finite deviations from the area law contain important information on the physics of the continuum quantum field theory. I will show how general properties of quantum entropy applied to these finite terms give a proof of Bekenstein’s universal bound on entropy by the product of energy and size. I will also discuss how the entropy contained in vacuum fluctuations give a meassure of the irreversibility of the renormalization group in low-dimensional quantum field theories. [recorded movie]	Herzog
May 6	graduate director	Graduate Awards Colloquium [recorded movie]	-