Department Calendar

November 2018

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Martin Claassen, Flatiron Institute

Martin Claassen, Flatiron Institute

Date: 
Fri, 11/02/2018 - 5:00pm
Location: 
11M Conference Room – North West Corner

 

“Universal Optical Control of Chiral Superconductors and Majorana Modes”

Chiral superconductors are a novel class of unconventional superconductors that host topologically protected chiral Majorana fermions at interfaces and domain walls, with great potential for topological quantum computing. In this talk, I will show that the out-of-equilibrium superconducting state in such materials is itself described by a Bloch vector in analogy to a qubit, which can be controlled all-optically on ultrafast time scales. The mechanism is universal and permits a dynamical change of handedness of the condensate, relying on transient dynamical breaking of lattice rotation, mirror or time-reversal symmetries via choice of pump pulse polarization to enable arbitrary rotations of the Bloch vector. The underlying physics can be intuitively understood in terms of transient Floquet dynamics, however the mechanism extends to ultrafast time scales, and importantly the engineered state persists after the pump is switched off. We demonstrate that these novel phenomena should appear in graphene and magic-angle twisted bilayer graphene (TBG), as well as Sr2RuO4, as candidate chiral d+id and p+ip superconductors, and show that chiral superconductivity can be detected in time-resolved pump-probe measurements.

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11/02/2018 - 5:00pm
 
 
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Ira Rothstein, Carnegie Mellon University

Ira Rothstein, Carnegie Mellon University

Date: 
Mon, 11/05/2018 - 2:10pm
Location: 
Pupin Hall Theory Center, 8th Floor

 

"The structure of the gravitational S matrix and precision gravity wave astronomy"

Effective field theory has proven to be a power tool in generating precise predictions for gravitational inspirals. In this talk I will discuss how our improved understanding of the gravitational S matrix can stream line calculations of both conservative and non-conservative dynamics.

About the speaker

Ira Rothstein's research includes diverse topics in elementary particle physics, gravity wave physics, astrophysics/cosmology and QCD. In the realm of high energy physics, Ira's interest involves using the data from the LHC to explain the origin of mass and the nature of the dark matter. He has worked on various topics in this field ranging from theories of extra dimensions to calculating Higgs boson production rates. Recently, Ira spent time working on using ideas developed in quantum field theory to calculate classical gravity wave profiles for inspiralling black holes. Using these techniques, Ira and his group have been able to calculate the effects of black hole spin on the predicted wave forms which are being measured at the LIGO experiment. Ira has also been working on effective field theory techniques to find systematic ways of calculating strong interaction observables at high energies.

More details can be found here.

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11/05/2018 - 2:10pm
 
No Physics Colloquium today (November 5)
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11/05/2018 - 4:15pm
 
 
 
Evegnii Narimanov, Purdue University

Evegnii Narimanov, Purdue University

Date: 
Thu, 11/08/2018 - 12:00pm
Location: 
705 Pupin Hall

 

"Optical Hyperspace: light in (meta)materials with hyperbolic dispersion"

The composites with opposite signs of the dielectric permittivity in two orthogonal directions, known as the hyperbolic metamaterials, represent a new "universality class" of optical media, with the light behavior which is qualitatively different from that in either metals or dielectrics. Propagating waves in such "electromagnetic hyperspace" do not suffer from the diffraction limit on the optical resolution, leading to the hyperlens - the device capable of producing magnified far-field images of subwavelength objects, while the broadband super-singularity of the photonic density of states in hyperbolic media results in a dramatic change in a variety of phenomena, from spontaneous emission to light propagation and scattering.

Title & abstract TBA

About the speaker

Evgenii Narimanov is professor of Electrical and Computer Engineering at Purdue University. He received his Ph.D. from Moscow Institute of Physics and Technology, and has held postdoctoral positions at Yale University and Bell Laboratories. Prof. Narimanov was a faculty member at the Electrical Engineering Department of Princeton University until 2007 when he moved to Purdue. Prof. Narimanov is a Fellow of the OSA (2009) and IEEE (2011).

More details can be found here.

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11/08/2018 - 12:00pm
 
Dimitri Basov, Columbia University

Dimitri Basov, Columbia University

Date: 
Fri, 11/09/2018 - 11:00am
Location: 
Pupin Hall Theory Center, 8th Floor

 

Dimitri Basov's research area is experimental condensed matter physics. Dimitri's research group employs optical methods to investigate new physics of quantum materials. Recent instrumental advances in infrared nano-optics, some of which have been pioneered in our group, enable unprecedented access to the optical effects at the nano-scale deep below the diffraction limit of light. The group exploits these instrumental innovations to explore new physical phenomena that are of technological relevance.

More details on Dimitri's research can be found here.

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11/09/2018 - 11:00am
 
Alexander B. Khanikaev, City College of New York, ASRC, & Graduate Center of CUNY

Alexander B. Khanikaev, City College of New York, ASRC, & Graduate Center of CUNY

Date: 
Fri, 11/09/2018 - 5:00pm
Location: 
11M North West Corner

 

"Topological states of light and sound"

The past three decades have witnessed the discovery of Quantum Hall Effect (QHE), Quantum Spin Hall Effect (QSHE) and Topological Insulators (TIs), which transformed our views on the quantum states of matter. These exotic states are characterized by insulating behavior in the bulk and the presence of the edge states contributing to charge or spin currents which persist even when the edge is distorted or contains impurities. In the last few years, a number of studies have shown that similar “robust” conducting edge states can be implemented in classical systems [1-4]. In this talk I will review development of this field with focus on photonic and acoustic topological structures with and without time-reversal symmetry that we have recently proposed [3-9]. I will discuss recent experimental realizations of topological order for electromagnetic waves with the use of bianisotropic metamaterials at microwave frequencies [4,6-8]. In addition, new practical designs of photonic and acoustic topological crystalline insulators and their possible applications will be presented. I will show that photonic and acoustic topological systems, with deliberately created distributions of synthetic gauge fields, offer an unprecedented platform for controlling light and sound, e.g. by enabling routing and steering of waves along arbitrarily shaped pathways without loss or backscattering [6] or controlling scattering of light [9]. I will also briefly discuss higher order topological states in acoustic systems.

[1] F. Haldane and S. Raghu, Phys. Rev. Lett. 100, 13904 (2008).
[3] Z. Wang, Y. Chong, J. D. Joannopoulos, and M. Soljacic, Nature 461, 772 (2009).
[4] A. B. Khanikaev, S. H. Mousavi, W.-K. Tse, M. Kargarian, A. H. MacDonald, G. Shvets, Nat. Mater. 12, 233 (2013).
[5] A. B. Khanikaev, R. Fleury, S. H. Mousavi, A. Alù, Nat. Comm. 6, 8260 (2015).
[6] X. Cheng, C. Jouvaud, Xiang Ni, S. H. Mousavi, A. Z. Genack, and A. B. Khanikaev, Nat. Mater, (2016). doi:10.1038/nmat4573
[7] A. Slobozhanyuk, S. H. Mousavi, X. Ni, D. Smirnova, Y. S. Kivshar, A. B. Khanikaev, Nature Photonics 11, 130–136 (2017).
[8] A. B. Khanikaev, G. Shvets, Nature Photonics 11 (12), 763 (2017).
[9] M. A. Gorlach, X. Ni, D. A. Smirnova, D. Korobkin, A. P. Slobozhanyuk, D. Zhirihin, P. A. Belov, A. Alù, A. B. Khanikaev, Nature Comm. 9 (1), 909 (2018)

About the speaker

Dr. Khanikaev’s group focuses on experimental research and theoretical studies of photonic nanostructures and metamaterials aiming to develop novel optical systems and devices with previously unattainable properties and useful functionalities. The research includes an interdisciplinary studies at the edge of optics and such disciplines as biology and condensed matter physics. One of the major research directions is engineering topological order and nonreciprocity in photonic nanostructures with magneto-optical and bianisotropic responses. The bio-oriented research program of the group is aiming to facilitate in-depth characterization of bio-molecules with the use infrared spectroscopy of plasmonic nanostructures and metamaterials

More details can be found here.

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11/09/2018 - 5:00pm
 
 
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Gianluca Zoccarato, UPENN

Gianluca Zoccarato, UPENN

Date: 
Mon, 11/12/2018 - 2:10pm
Location: 
Pupin Hall Theory Center, 8th Floor

 

"F-theory and dark energy"
I will present compactifications of F-theory a four dimensional spacetime with spatial slices that have the topology of 3-sphere. These solutions may be used as a starting point for solving some of the known problems of the cosmological constant. The 3-sphere is the target space of an SU(2) WZW model which allows for an exact worldsheet analysis. The compactification space is chosen to be a Spin(7) manifold thus giving "half-supersymmetry" in 4D. I will discuss cosmological solutions that resemble Einstein static Universe. These solutions are actually unstable and can either contract or expand, leading to possibly interesting cosmological scenarios. Finally I will discuss the implications of these scenarios for particle physics.

Title & abstract TBA

About the speaker

Gianluca's research interests include string phenomenology and string compactifications.

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11/12/2018 - 2:10pm
 
Luca Grandi, University of Chicago

Luca Grandi, University of Chicago

Date: 
Mon, 11/12/2018 - 4:15pm
Location: 
428 Pupin Hall

 

"The XENON Program: at the forefront of Dark Matter Direct Detection"

Dark Matter is out there, waiting to be detected. I will present the XENON way of doing it - i.e. with two-phase Time Projection Chambers (TPC) sensitive to possible dark matter interactions inside an ultra-low background Liquid Xenon (LXe) target. The XENON1T detector has been operating at Laboratory Nazionali del Gran Sasso since Spring 2016, and with 3.3 tons of xenon it is presently the largest LXe dark matter experiment in operation. I will guide you through the XENON1T science program, presenting the experimental challenges and the most recent results. Finally I will discuss the path towards its upgrade, XENONnT, presently under construction at Gran Sasso National Laboratory and with early science data expected in mid-2019.

About the speaker

Luca Grandi studies fundamental physics, of a type that is able to change one’s way of looking at the surrounding world and provide a deeper understanding of how nature works. He has also been attracted by small-scale, human-size experiments, and enjoys designing and operating detectors and analyzing their collected data. These interests led him toward the field of rare events physics and, more specifically, toward dark matter direct searches. This area of research has great potential for discovery and the capability of providing experimental results that affect the foundation of our physics theories.

To date, his activities have been focused on the development of liquid argon two-phase time projection chamber (TPC) technology for dark matter direct detection. He was involved in the design, construction, and operation of the WArP-2.3kg prototype, the first and only argon detector to have set a limit on the WIMP (weakly interacting massive particles) interaction rate. Together with colleagues from other institutions, he cofounded the DarkSide project, which combines two-phase argon and organic liquid scintillator technologies. DarkSide-50, the first physics detector of the DarkSide family, is being deployed at Gran Sasso Underground Laboratory in Italy, and has become an international collaboration involving other institutions from the United States and Europe.

Grandi completed his PhD course of study in physics at Pavia University in Italy. 

More details on Gary's research can be found here.

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11/12/2018 - 4:15pm
 
 
Kazu Terao, SLAC National Laboratory

Kazu Terao, SLAC National Laboratory

Date: 
Wed, 11/14/2018 - 1:00pm
Location: 
705 Pupin Hall

 

"Deep Neural Network Applications for Liquid Argon Time Projection Chamber Data Reconstruction"

Liquid Argon Time Projection Chambers (LArTPCs) are capable of recording images of charged particle tracks with breathtaking resolution.  Such detailed information will allow LArTPCs to perform accurate particle identification and calorimetry, making it the detector of choice for many current and future neutrino experiments.  However, analyzing such images can be challenging, requiring the development of many algorithms to identify and assemble features of the events in order to reconstruct neutrino interactions.  In the recent years, we have been investigating a new approach using deep neural networks (DNNs), a modern solution to a pattern recognition for image-like data in the field of Computer Vision. A modern DNN can be applied for various types of problems such as data reconstruction tasks including interaction vertex finding, pixel clustering, and particle/topology type identification. We have developed a small inter-experiment collaboration to share generic software tools and algorithms development effort that can be applied to non-LArTPC imaging detectors. In this talk I will discuss the challenges of LArTPC data reconstruction, recent work and future plans for developing a full LArTPC data reconstruction chain using DNNs.

About the speaker

Kazu is currently involved in the MicroBooNE experiment as an associate staff scientist member in the Elementary Particle Physics (EPP) division at SLAC national accelerator laboratory. Previously he worked on the same experiment was a post-doctoral research scientist at Nevis Laboratories at Columbia University. Before MicroBooNE, Kazu worked on Double Chooz during my Ph.D at MIT, and KamLAND while at U.C. Berkeley for his undergraduate studies.

Currently, Kazu's focus is to apply a machine learning technique, in particular deep neural networks to perform data recontruction tasks and physics analysis.

More details can be found here.

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11/14/2018 - 1:00pm
 
 
Leonid Rokhinson, Purdue

Leonid Rokhinson, Purdue

Date: 
Fri, 11/16/2018 - 5:00pm
Location: 
11M North West Corner

 

Nano-Optics Seminar
"Experimental search for non-Abelian excitations"

I will start with an introduction into the physics of Majorana fermions in semiconductor/superconductor hybrids and description of our experiments where the fractional ac Josephson effect, a hallmark of topological matter, has been observed. I will briefly discuss challenges facing the field which make manipulation and demonstration of non-Abelian statistics extremely difficult.

In the second part I will introduce a new platform based on spin transitions in the fractional quantum Hall effect regime where parafermions - higher order non-abelian excitations - can be realized. Local (gate) control of spin transition allows formation of isolated domain walls, which consist of counter-propagating edge states of opposite polarization with fractional charge excitations. When superconductivity is induced into such a domain wall from superconducting contacts via proximity effect, parafermions are expected to be formed at the domain wall boundaries. In a multi-gate device a re-configurable network of domain walls can be formed allowing creation, braiding, manipulation and fusion of parafermions. In respect to the quantum computing application parafermons are more computationally intense than Majoranas and are a building block for Fibonacci fermions, even high order non-Abelian particles that can perform universal gate operations within the topologically protected subspace.
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11/16/2018 - 5:00pm
 
 
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Hayden Lee, Harvard University

Hayden Lee, Harvard University

Date: 
Mon, 11/19/2018 - 2:10pm
Location: 
Pupin Hall Theory Center, 8th Floor

 

"The Cosmological Bootstrap: Inflationary Correlators from Symmetries and Singularities"

In flat space, symmetries and singularities can be used to fully determine the structure of 4-particle scattering amplitudes at tree level. In this talk, I will describe how a similar logic can be used to uniquely fix the structure of tree-level inflationary correlation functions with approximate conformal symmetry, without reference to a Lagrangian description. I will present analytic solutions for the inflationary 3- and 4-point functions of conformally-coupled/massless scalars with arbitrary spin exchange, and show how these objects are related to each other via simple differential operators. As a result, the most general 3- and 4-point functions arising from weakly broken conformal symmetry are completely characterized by two basis functions up to coupling constants. Moreover, these inflationary correlators “contain” flat-space scattering amplitudes via an analytic continuation, providing a nontrivial link between scattering in flat space and particle production in curved space.

Title & abstract TBA

About the speaker

Hayden Lee is currently a Postdoc in Cora Dvorkin's research group at Harvard University.

More details can be found here.

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11/19/2018 - 2:10pm
 
Jainendra Jain, Penn State University

Jainendra Jain, Penn State University

Date: 
Mon, 11/19/2018 - 4:15pm
Location: 
428 Pupin Hall

 

"The cool world of electrons trapped in a magnetic vortex"

When electrons in two dimensions are cooled to near absolute zero and exposed to a strong magnetic field, the repulsive Coulomb interaction traps them into quantized magnetic vortices to create topological particles called composite fermions. These are responsible for the unexpected phenomenology of this state, including the celebrated fractional quantum Hall effect. After providing a simple introduction to this physics, I shall discuss recent work leading to detailed quantitative comparisons with experiments. I shall also describe how certain experimentally observed states that do not fit into the composite fermion paradigm find possible explanation in terms of the so-called parton construction of the fractional quantum Hall effect.

About the speaker

Jain is a quantum physicist in the field of condensed matter theory with interests in the area of strongly interacting electronic systems in low dimensions. As the originator of the exotic particles called composite fermions, he developed the composite fermion theory of the fractional quantum Hall effect and unified the fractional and the integral quantum Hall effects. He was a co-recipient of the 2002 Oliver E Buckley Prize, and is a Fellow of the American Physical Society, American Association for the Advancement of Science, and the American Academy of Arts and Sciences. He is the Evan Pugh University Professor and the Erwin W. Mueller Professor of Physics at Penn State, and the Infosys Visiting Chair at the Indian Institute of Science, Bangalore. His writings include a monograph Composite Fermions, published in 2007 by the Cambridge University Press.

More details on Jain's research can be found here.

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11/19/2018 - 4:15pm
 
 
 
 
 
 
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Sera Cremonini, Lehigh University

Sera Cremonini, Lehigh University

Date: 
Mon, 11/26/2018 - 2:10pm
Location: 
Pupin Hall Theory Center, 8th Floor

 

Title & abstract TBA

About the speaker

Sera Cremonini is a theoretical particle physicist, working on various aspects of string theory, quantum field theory and cosmology.

More details can be found here.

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11/26/2018 - 2:10pm
 
Albert Young, North Carolina State University/Triangle Universities Nuclear Laboratory for the UCNtau Collaboration

Albert Young, North Carolina State University/Triangle Universities Nuclear Laboratory for the UCNtau Collaboration

Date: 
Mon, 11/26/2018 - 4:15pm
Location: 
428 Pupin Hall

 

"The neutron lifetime challenge: particle physics with neutrons in bottles and beams"

Measurements of neutron decay provide us with our most precise characterization of components of the charged weak current of the nucleon and are playing an important role in the broad band constraints from beta decay at the 11 TeV level on new physics.  In the standard model, two coupling constants (for vector and axial-vector couplings) are required to specify the neutron lifetime and the angular correlations of the decay products.  Although there has been striking progress over the past two years in the status of the axial coupling constant on both experimental and theoretical fronts, the experimental status of the lifetime is not so clear, with a roughly 4 sigma discrepancy evident between experiments made with stored ultracold neutrons and those made with neutron beams.  In this presentation, the status of storage experiments made with ultracold neutrons and experiments made with cold neutron beams is reviewed, highlighting recent experimental results, the origin of key sources of systematic uncertainty and how the community has moved to address these issues.  We in the UCNtau collaboration have developed an experiment to store ultracold neutrons in an asymmetric magnetic trap at the Los Alamos Neutron Science Center, reducing losses to the point where, if neutrons didn’t decay, their storage time would be over a month (limited by scattering from ambient gas in our vacuum system).  Our most recent results, which  reinforce the discrepancy between storage and beam experiments, are presented, as well as our attempts to experimentally constrain explanations of the lifetime discrepancy through decays to “dark” particles.

This research was supported by the Nuclear Physics Division of the National Science Foundation, the Department of Energy through the Low Energy Fundamental Symmetries Division, and through LDRD support at Los Alamos.

About the speaker

Albert Young received his PhD in 1990 from Harvard University in experimental atomic physics. He spent 1990 to 1992 at the California Institute of Technology as a research associate in Felix Boehm’s group, and then moved to Princeton where he stayed for the next eight years, first as a research associate, then as a lecturer, and finally as an assistant professor from 1996 to 2000. He joined NC State University in 2000 as assistant professor. He was promoted to associate professor in 2001 and professor in 2005.

He developed several different methods for optically orienting nuclei and participated in a variety of atomic, nuclear and particle physics experiments, typically to test some aspect of the standard electroweak theory of particle physics. He helped develop a prototype solid deuterium source of ultracold neutrons at Los Alamos that became the basis for a similar project at the PULSTAR reactor on the NC State University campus. He is a member of the American Physical Society.

More details on Gary's research can be found here.

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11/26/2018 - 4:15pm
 
 
Stephanie Wissel, Cal Poly, San Luis Obispo

Stephanie Wissel, Cal Poly, San Luis Obispo

Date: 
Wed, 11/28/2018 - 1:00pm
Location: 
705 Pupin Hall

 

Title & abstract TBA

About the speaker

Stephanie Wissel is an Assistant Professor in Physics at the California Polytechnic State University in San Luis Obispo (Cal Poly).

Stephanie attended the the University of Dallas, graduating with a bachelor's degree in physics in 2004 and then earning her master's degree in 2005 and a doctorate in 2010 at the University of Chicago.  For her dissertation she developed a technique for measuring the composition of cosmic rays using imaging Cherenkov telescopes, like VERITAS and TrICE.

At Cal Poly, Stephanie specializes in experimental particle astrophysics, searching for the highest energy neutrinos and cosmic rays. Recent work consists of the radio detection of high-energy particles working on ANITA as a postdoc at the University of California, Los Angeles. Stephanie is also a member of the ARA collaboration and also did a postdoc in science education at the Princeton Plasma Physics Laboratory, where she taught, developed curricula and exhibits, and worked with educators.

More details can be found here.

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11/28/2018 - 1:00pm
 
Tyrel McQueen, Johns Hopkins University

Tyrel McQueen, Johns Hopkins University

Date: 
Thu, 11/29/2018 - 12:00pm
Location: 
705 Pupin Hall

 

Title & abstract TBA

About the speaker

The McQueen Laboratory is a solid state chemistry materials research group focused on the discovery of new phenomena through the design and synthesis of new materials. The lab aims to achieve the next generation of materials revolutions by combining the development of new synthetic techniques with advances in measurement and analysis methods to discover, design, and control materials with exotic electronic states of matter.

More details on Tyrel and his group can be found here.

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11/29/2018 - 12:00pm
 
 
 
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