Department Calendar

March 2019

Sun Mon Tue Wed Thu Fri Sat
24
25
26
27
28
1
2
 
 
 
 
 
 
 
3
4
5
6
7
8
9
 
Thesis Defense - Felix Clark

Thesis Defense - Felix Clark

Date: 
Mon, 03/04/2019 - 10:30am
Location: 
705 Pupin Hall

 

"Femtoscopic signatures of small QGP droplets in proton-lead collisions at the Large Hadron Collider."

Dissertation Sponsor and Research Advisor: Professor Brian Cole

 

 
To RSVP for this talk please contact ma3167@columbia.edu
Add to calendar Add to Google Calendar
03/04/2019 - 10:30am
 
Kathryn Zurek - Lawrence Berkeley National Lab

Kathryn Zurek - Lawrence Berkeley National Lab

Date: 
Mon, 03/04/2019 - 12:30pm
Location: 
Pupin Hall Theory Center, 8th Floor

 

“Broadening the Searchlight: New Ideas in Dark Matter Detection”

Searches for massive dark matter have largely focused on a mass window near the weak scale, the so-called “WIMP window".  This window is, however, becoming increasingly closed by both the LHC and the unprecedented sensitivity of direct detection experiments.  At the same time, theoretical work in recent years has shown lighter dark matter candidates in a hidden sector are theoretically well-motivated, natural and arise generically in many theories beyond the standard model.  New ideas are needed to search for dark matter with mass below a GeV and as light as the warm dark matter limit of a keV.  We propose new ideas to search for such light dark matter with superconductors, Dirac materials, superfluid helium, and polar crystals.  We show that these same experiments, through inelastic processes, may also be sensitive to dark matter with masses in the meV to keV mass window, broadening the mass reach to light dark matter by many orders of magnitude.

About the speaker

Kathryn has a wide range of interests, mostly focused at the boundary of particle physics with astrophysics and cosmology. Her work spans both studies of new physics signatures at colliders, as well as astrophysical searches for dark matter (DM) and physics beyond the Standard Model in the neutrino sector. Kathryn originated Hidden Valley models as a portal to hidden world signatures, including displaced decays, at colliders. More recently, she has been most active in the study of DM, working on theories of DM and ways that we can detect it in the lab by DM-nucleus interactions, at colliders through high energy collisions, and in the galaxy by DM self-annihilations. Kathryn introduced simple, viable models of Asymmetric Dark Matter as an alternative to the standard paradigm of Weakly Interacting Massive Particles, and developed the cosmology of these models. Recently, she has been studying the evolution of scalar fields (such as the Higgs boson) with a potential instability during inflation.

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

Add to calendar Add to Google Calendar
03/04/2019 - 12:30pm
 
CANCELED: Kin-Wang Ng - Academia Sinica, Taiwan

CANCELED: Kin-Wang Ng - Academia Sinica, Taiwan

Date: 
Mon, 03/04/2019 - 2:10pm
Location: 
Pupin Hall Theory Center, 8th Floor

** Today's Theory Seminar with Kin-Wang Ng will not take place.  A new date has not been determined **

 

"Inflation, primordial black holes, and gravitational waves"

We discuss the production of primordial black holes and associated gravitational waves in inflation models. These primordial black holes may constitute the dark matter and the associated gravitational waves may be detectable by pulsar timing arrays and gravity-wave interferometry experiments.

About the speaker

Kin-Wang Ng's research interest involve particle astrophysics and cosmology, early universe, inflationary cosmology and quantum fluctuations, dark matter and cosmic microwave background.

More details on Kin-Wang's research can be found here.

Add to calendar Add to Google Calendar
03/04/2019 - 2:10pm
 
 
 
 
Ana Asenjo Garcia - Columbia

Ana Asenjo Garcia - Columbia

Date: 
Fri, 03/08/2019 - 11:00am
Location: 
Pupin Hall Theory Center, 8th Floor

 

"Correlated physics in arrays of quantum dipoles"

Ana Asenjo-Garcia works at the interface between quantum optics, atomic physics and open quantum systems. In this talk, she will discuss her main research interests, which orbit around the study of many-body physics in dissipative scenarios. In particular, she will provide a comprehensive look into the physics of subradiance, an emergent form of correlated dissipation that gives rise to long-lived states in atomic arrays. She will also discuss how this phenomenon can be exploited to realize efficient implementations of quantum information protocols.

About the speaker

Ana Asenjo Garcia, an assistant professor at the physics department of Columbia University.  Ana focus is theoretical research on interactions between light and quantum matter. 

Add to calendar Add to Google Calendar
03/08/2019 - 11:00am
 
 
10
11
12
13
14
15
16
 
James McIver - Max Planck Institute

James McIver - Max Planck Institute

Date: 
Mon, 03/11/2019 - 10:00am
Location: 
705 Pupin Hall

 

"Femtosecond science on-chip: Capturing light-induced anomalous Hall currents in graphene"

Many striking non-equilibrium phenomena have been discovered or predicted in quantum solids driven by femtosecond pulses of light, ranging from photo-induced superconductivity [1] to Floquet-engineered topological phases [2]. These effects are expected to lead to dramatic changes in electrical transport, but can only be comprehensively characterized or functionalized with a direct interface to electrical devices that operate at ultrafast speeds. This can be accomplished by adopting an ultrafast optoelectronic device architecture based on laser-triggered photoconductive switches. In this talk, I will present results demonstrating that a mid-infrared femtosecond pulse of circularly polarized light induces an anomalous Hall effect in monolayer graphene. The dependence of the effect on a gate potential used to tune the Fermi level reveals multiple features that directly reflect the emergence of a photon-dressed topological band structure in graphene, similar to the one originally proposed by Haldane [3], including a ∼60 meV wide plateau centered at the Dirac point. When the Fermi level lies within this plateau, the anomalous Hall conductance approaches 2e2/h. 

[1] D. Fausti et al.  Science 331, 189-191 (2011) 
[2] T. Oka & H. Aoki Phys. Rev. B 79, 081406 (2009)
[3] F.D.M. Haldane, Phys. Rev. Lett. 61, 2015-2018 (1988)

About the speaker

James McIver is a condensed matter physicist at the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg. He received his PhD in physics from Harvard University and is the recipient of an NSF graduate research fellowship and a Humboldt postdoctoral fellowship. His work focuses on understanding and controlling the dynamical transport properties of optically-driven functional materials using on-chip femtosecond electronics.

Add to calendar Add to Google Calendar
03/11/2019 - 10:00am
 
Christoph Lehner - Brookhaven National Lab & University of Regensburg

Christoph Lehner - Brookhaven National Lab & University of Regensburg

Date: 
Mon, 03/11/2019 - 12:30pm
Location: 
Pupin Hall Theory Center, 8th Floor

 

"The anomalous magnetic moment of the muon"

Since the final report of the BNL E821 experiment in 2006 the muon’s anomalous magnetic moment has exhibited a tension with the standard model theory calculation of 2 to 3 sigma, possibly indicating contributions from new physics.  Refinements on the theory side have elevated the tension to around 3.7 sigma as of 2018 with experimental and theory uncertainties approximately balanced.  The new Fermilab E989 experiment aims to reduce the experimental uncertainty by a factor of four with first results anticipated in the summer of 2019.  A vigorous theory effort is underway to match this improvement in order to clarify the tension over the next years.  I will report on the current theory status and expected future improvements.

About the speaker

Christoph Lehner received his PhD from University of Regensburg, Germany, in 2010 and is currently a Scientist at Brookhaven National Lab and a Professor at University of Regensburg.

Christoph's honors include Ken Wilson Lattice Award in 2012 and a DOE Early Career Award in 2016.

Add to calendar Add to Google Calendar
03/11/2019 - 12:30pm
 
Ken Van Tilburg - IAS & NYU

Ken Van Tilburg - IAS & NYU

Date: 
Mon, 03/11/2019 - 2:10pm
Location: 
Pupin Hall Theory Center, 8th Floor

 

"Searches for light bosonic dark matter"

If the dark matter is made up of a bosonic particle, it can be ultralight, with a mass potentially much below that of ordinary particles. Moduli fields, whose values could set couplings and masses of known particles, are good candidates for such light dark matter. Their abundance in our Universe would manifest itself as tiny fractional oscillations of Standard Model parameters, such as the electron mass or the fine-structure constant, in turn modulating length and time scales of atoms. Rods and clocks, used for gedanken experiments in the development of relativity theory, have since transformed into actual precision instruments. The size of acoustic resonators and the frequency of atomic transitions can now be measured to 1 part in 10^24 and 10^18, respectively, and thus constitute sensitive probes of moduli over a mass range of 10^-22 eV to 10^-6 eV.

In addition, I will present a proposal for another class of bosonic dark matter detectors based on resonant absorption onto a gas of small polyatomic molecules. Bosonic DM acts on the molecules as a narrow-band perturbation, like an intense but weakly coupled laser. The excited molecules emit the absorbed energy into fluorescence photons that are picked up by sensitive photodetectors with low dark count rates. This setup is sensitive to any DM candidate that couples to electrons, photons, and nuclei, and may improve on current searches by several orders of magnitude in coupling for DM masses between 0.2 eV and 20 eV. This type of detector has excellent intrinsic energy resolution, along with several control variables---pressure, temperature, external electromagnetic fields, molecular species/isotopes---that allow for powerful background rejection methods as well as precision studies of a potential DM signal. The proposed experiment does not require usage of novel exotic materials or futuristic technologies, relying instead on the well-established field of molecular spectroscopy, and on recent advances in single-photon detection. Cooperative radiation effects, which arise due to the large spatial coherence of the nonrelativistic DM field in certain detector geometries, can tightly focus the DM-induced emission photons in a direction that depends on the DM's velocity, permitting a detailed reconstruction of the full 3D velocity distribution in our Galactic neighborhood, as well as further background rejection.

About the speaker

Ken Van Tilburg’s research covers various aspects of particle physics phenomenology, in particular model building and novel techniques to look for new physics. His current work focuses on the development of precision search strategies for dark matter, gravitational waves, new forces, and other manifestations of weakly coupled physics both in and beyond the Standard Model.

More information on Ken's research can be found here.

Add to calendar Add to Google Calendar
03/11/2019 - 2:10pm
 
Archana Raja - UC Berkeley

Archana Raja - UC Berkeley

Date: 
Tue, 03/12/2019 - 10:00am
Location: 
705 Pupin Hall

 

"Tuning energy levels and energy flow in nanomaterials through the external environment"

Light absorbed by a semiconductor is stored as electronic excitations in the form of bound electron-hole pairs, also known as excitons. There is a rich variety of semiconductor nanostructures available today for the design of novel material systems and interfaces with tailor-made functionalities. In particular, atomically thin two-dimensional (2D) materials such as graphene and transition metal dichalcogenide (TMDC) monolayers exhibit extraordinary optical and electrical properties. For such materials, with thicknesses below 1 nanometer, I will show that the external dielectric environment strongly influences their intrinsic electronic states [1], energy transfer processes [2], and excited-state dynamics [3].  I will also briefly discuss new experimental approaches to the study of these phenomena and the associated ultrafast dynamics. In addition to the intrinsic scientific interest in understanding materials in this distinctive regime, such control offers a non-invasive approach to engineer material properties and dynamics by tuning the local environment rather than the material itself, yielding a new paradigm for nanoscale devices and energy conversion processes.

[1] A. Raja et al. Coulomb engineering of the bandgap and excitons in two-dimensional materials. Nature Communications 8, 15251 (2017)
[2[ A. Raja et al. Energy transfer from quantum dots to graphene and MoS2: the role of absorption and screening in two-dimensional materials. Nano Letters 16, 2328–2333 (2016)
[3] A. Raja et al. Enhancement of Exciton−Phonon Scattering from Monolayer to Bilayer WS2. Nano Letters 18, 6135-6143 (2018)
 

About the speaker

Archana Raja completed her PhD in Chemical Physics from Columbia University under the supervision of Profs. Tony Heinz and Louis Brus in 2016. After spending a year as a postdoc in the Applied Physics department at Stanford University, she joined the Kavli Energy and Nanoscience Institute at UC Berkeley as a Heising-Simons postdoctoral fellow, in the group of Prof. Paul Alivisatos.

Add to calendar Add to Google Calendar
03/12/2019 - 10:00am
 
Anshul Kogar - MIT

Anshul Kogar - MIT

Date: 
Wed, 03/13/2019 - 10:00am
Location: 
705 Pupin Hall

 

"Light-Matter Interaction in Charge Density Waves"

When electrons in a solid are excited with light, they can alter the free energy landscape and access regions that are beyond reach in thermal equilibrium. This accessibility becomes of importance in the presence of phase competition, when one state of matter is favored over another by only a small energy scale that, in principle, is surmountable with light. In this talk, I will discuss a few of our recent ultrafast electron diffraction results on charge density wave (CDW) materials showing that, under far-from-equilibrium conditions, we observe strong evidence for topological defects. These defects are crucial in explaining how the amplitude of the CDW recovers well before long-range phase coherence. I will also show that in certain CDW materials, these defects can be manipulated with light to form metastable structures. Lastly, I will show that light can be used to unleash a CDW that is not present in equilibrium.

About the speaker

Anshul did his undergraduate studies at UCLA before moving onto get his PhD from the Univeristy of Illinois. There, he developed a new experimental method to probe condensed matter systems which now goes by the name of momentum-resolved electron energy loss spectroscopy or M-EELS. Using this method, he showed that the charge density wave transition in 1T-TiSe2 is driven by exciton condensation. Since then, he has pursued postdoctoral research studies at MIT using ultrafast electron diffraction studies on various charge density wave systems.

Add to calendar Add to Google Calendar
03/13/2019 - 10:00am
 
Felix Aharonian - Dublin Institute for Advanced Studies

Felix Aharonian - Dublin Institute for Advanced Studies

Date: 
Wed, 03/13/2019 - 1:00pm
Location: 
705 Pupin Hall

 

"Ground-based gamma-ray astronomy: Scientific objectives in different energy bands"

I will highlight the status of ground-based gamma-ray astronomy and discuss the major scientific objectives of the field in different energy band.

About the speaker

Felix Aharonian graduated from Moscow Engineering-Physics Institute in Nuclear and Particle Physics in 1975. He obtained his PhD degree in the same Institute in 1979. He then worked in the Yerevan Physics Institute (Armenia/USSR) from 1979 to 1991, in the Enrico Fermi Institute of the University of Chicago (USA) from 1991 to 1992, in the Max Planck Institut fuer Kernphysik (MPIK) in Heidelberg (Germany) from 1992 to 2006. In 2006 he was appointed as Professor of the Astronomy and Astrophysics Section of the School of Cosmic Physics. In parallel, he leads the High Energy Astrophysics Theory Group of MPIK/Heidelberg with a status of External Member of the Institute.

More details on Felix's research group can be found here.

 

*Lunch will be provided for attendees

Add to calendar Add to Google Calendar
03/13/2019 - 1:00pm
 
Edbert Sie - Stanford University

Edbert Sie - Stanford University

Date: 
Thu, 03/14/2019 - 10:00am
Location: 
705 Pupin Hall

 

"Ultrafast Optical Control of Quantum Material Symmetry"

A primary goal of modern condensed matter physics is to realize and control novel phases of quantum matter. Although many approaches using material synthesis and static fields have been used at thermal equilibrium, there exists a vast unexplored landscape and associated symmetries at non-equilibrium. Here we can use light to manipulate the space-time symmetries in materials and realize new quantum phenomena that were previously inaccessible. First, we apply terahertz laser pulses to switch the inversion lattice symmetry and induce a topological transition in the Weyl semimetal WTe2. The optically-induced change of lattice structure is crystallographically probed using time-resolved electron diffraction. Second, we apply helical laser pulses to break time-reversal symmetry and tune the energy of specific valleys in monolayer WS2. This approach offers non-equilibrium pathways to control quantum properties of matter on ultrafast timescales.

About the speaker

Edbert Sie is currently a Postdoctoral Geballe Fellow at Stanford University, in the group of Prof. Aaron Lindenberg. He received his PhD in Physics in 2017 at the Massachusetts Institute of Technology (MIT), under the supervision of Prof. Nuh Gedik. His research interests focus on engineering novel phases of quantum materials with light at the atomic length scale and on femtosecond time scale. He is a recipient of the APS Richard L. Green Dissertation Award in Experimental Condensed Matter Physics (2019), Springer Nature Thesis Award (2017), and Stanford GLAM Fellowship (2017).

Add to calendar Add to Google Calendar
03/14/2019 - 10:00am
 
Daniel Gruen - Stanford

Daniel Gruen - Stanford

Date: 
Thu, 03/14/2019 - 11:00am
Location: 
Pupin Hall Theory Center, 8th Floor

 

"Cosmology from structure beyond the power spectrum"

The growth of structure in our Universe produces rich data that inform our understanding of cosmology and astrophysics. Much of this information is contained in non-Gaussian fluctuations of matter density. I will give an overview of cosmology results by the Dark Energy Survey (DES) that are driven by the weak gravitational lensing measurements of these non-Gaussian features. My focus will be on results from the full probability distribution function of matter and galaxy density, and from clusters of galaxies. These features allow key tests of our understanding of cosmology and structure formation, yet pose significant challenges in data processing, measurement, and modeling. To fulfill the promise of structure as a decisive test of cosmology, we will have to devise new methods of jointly and fully analyzing the unprecedented data collected by upcoming astronomical surveys.

About the speaker

Daniel Gruen completed his undergraduate and graduate studies at LMU Munich, with a master's thesis at UPenn, prior to his current appointment as Postoctoral Reseracher and Einstein Fellow at Stanford.  Daniel works on weak gravitational lensing measurements of structure as a probe of cosmology and co-coordinate the Dark Energy Survey working group on this subject.

Add to calendar Add to Google Calendar
03/14/2019 - 11:00am
 
Mohammad Hafezi - University of Maryland

Mohammad Hafezi - University of Maryland

Date: 
Thu, 03/14/2019 - 4:00pm
Location: 
705 Pupin Hall

 

"Topological photonics: from classical to quantum"

There are many intriguing physical phenomena which are associated with topological features --- global properties that are not discernible locally. The best-known examples are quantum Hall effects in electronic systems, where insensitivity to local properties manifests itself as conductance through edge states which are insensitive to defects and disorder. In the talk, we first discuss how similar physics can be observed for photons; specifically, how various quantum Hall Hamiltonians can be simulated in an optical system. We report on the imaging and measurement of topological photonic edge states and the generation of correlated-photon pairs, in silicon photonics platform. 

We then discuss how strong interaction between photons can be created by the integration of topological photonic structures with solid-state quantum emitters. Specifically, we demonstrate the chiral emission of a quantum emitter into topological edge modes and establish their robustness against sharp bends. This approach may enable the creation of fractional quantum Hall states of light and also quantum optical devices with built-in protection.

In the end, we describe how photons, in a different role, could be exploited to probe and manipulate topological electronic states. In particular, we theoretically investigate the realization of a two-component fractional quantum Hall phases in monolayer graphene by optically driving the system, in a non-equilibrium regime. Moreover, we discuss how quantum optics toolbox can be applied to such correlated states of electrons.

About the speaker

Mohammad Hafezi studied for two years at Sharif University before completing his undergraduate degree at École Polytechnique in 2003. He received his Ph.D. in Physics from Harvard University in 2009. He was a senior research associate at the Joint Quantum Institute before joining UMD as a faculty. His group aims at the theoretical and experimental investigation of quantum properties of light-matter interaction, for applications in classical and quantum information processing and sensing. He received a Sloan Research Fellowship and Office of Naval Research Young Investigator award in 2015.

Add to calendar Add to Google Calendar
03/14/2019 - 4:00pm
 
Evan Hall - MIT

Evan Hall - MIT

Date: 
Thu, 03/14/2019 - 4:00pm
Location: 
Pupin Hall Theory Center, 8th Floor

 

"The Future of Ground-Based Gravitational-Wave Detection"

Gravitational-wave astrophysics has come to fruition with the first observations of binary black hole coalescences and the multimessenger observation of a binary neutron star coalescence. However, current detectors can access only a small fraction of the gravitational-wave universe, and the fine details of gravitational-wave signals remain buried in noise. A new generation of detectors, employing new technologies and larger facilities, will be able to collect events all the way back to the cosmic dark ages, and record nearby events with great precision. This will enhance our understanding of the history of the universe, enable new tests of general relativity, and uncover the behavior of nuclear matter in extreme environments. I will lay out the roadmap for ground-based gravitational-wave detection and discuss the technological challenges needed to make new detectors a reality.

About the speaker

Evan Hall received his BA in physics from the University of Chicago in 2012 and his PhD in physics in 2017 from the California Institute of Technology.  At Caltech Evan was a graduate student in the LIGO Laboratory under Prof. Rana Adhikari. Evan worked on controls and sensitivity improvements at the LIGO Hanford Observatory for the first and second Advanced LIGO observing runs; he also worked on tabletop investigations into new mirror materials for high-precision interferometry. As a postdoctoral fellow at the Massachusetts Institute of Technology, Evan has focused on the design and planning of next-generation gravitational-wave detectors.

Add to calendar Add to Google Calendar
03/14/2019 - 4:00pm
 
Jia Liu - Princeton

Jia Liu - Princeton

Date: 
Fri, 03/15/2019 - 11:00am
Location: 
705 Pupin Hall
Please note the location change to 705 Pupin Hall
"Neutrino Mass from Cosmology"

Ghostly neutrino particles continue to bring surprises to fundamental physics, from their existence to the phenomenon of neutrino oscillation which implies that their masses are nonzero. Their exact masses, among the most curious unknowns beyond the Standard Model of particle physics, can soon be probed by the joint analysis of upcoming cosmological surveys including LSST, Euclid, WFIRST, Simons Observatory, and CMB-S4. In this talk, I will first discuss ongoing work studying the effects of massive neutrinos. I will then turn the focus to my major efforts of modeling the challenging nonlinear regime of cosmic structures (<10 Mpc) where neutrino effects are the strongest. Finally, I will draw a roadmap to pin down the neutrino mass over the next decade.

About the speaker

Jia Liu is an NSF postdoctoral fellow at Princeton University. She obtained her PhD from Columbia University in 2016. Jia's research focuses on the large scale structure of our universe –– dark matter, halos, filaments, and voids. She aims to elucidate fundamental physics, such as the nature of dark energy and neutrino mass, using cosmological observations of the cosmic microwave background and galaxies together with state-of-the-art numerical simulations. Jia is a member of the LSST and Simons Observatory, leading efforts on higher-order statistics and joint cosmological constraints on neutrino mass.

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

Add to calendar Add to Google Calendar
03/15/2019 - 11:00am
 
Charles Black - BNL

Charles Black - BNL

Date: 
Fri, 03/15/2019 - 5:00pm
Location: 
11M North West Corner
Nano Optics Seminar

Charles Black

Director, Center for Functional Nanomaterials, Brookhaven National Laboratory

"Nanoscience and Quantum Information Science at the Center for Functional Nanomaterials, a National Scientific User Facility"

The Center for Functional Nanomaterials (CFN) is a national scientific user facility operated at Brookhaven National Laboratory for the U.S. Department of Energy.  One of five DOE Nanoscale Science Research Centers, the CFN offers external users a supported research experience with top-caliber scientists and access to state-of-the-art instrumentation at no cost via a peer- reviewed proposal process. The CFN mission is advancing nanoscience to impact society, by being an essential resource for the nanoscience community and producing breakthroughs in nanomaterials research.  In this presentation I will give an overview of the scientific facilities, describe examples of user and staff research, and summarize the process of becoming a CFN user.

I will also provide a brief overview of the system of DOE National Laboratories, their scientific mission, and the role of the Labs in the research ecosystem of the United States.   For students and early career researchers, I will share perspectives on the unique aspects of pursuing a research career in the National Labs.

Finally, I will discuss the U.S. National Quantum Initiative Act passed by Congress in late 2018 and the roles for different federal agencies.  Brookhaven Lab has mobilized in broad support of multiple aspects of this important national initiative, including: quantum technologies and experimental methods, computer and computational science, and basic materials science.  The CFN and the National Synchrotron Light Source II (NSLS-II) are integral to Brookhaven’s contributions to quantum information science, bringing advanced capabilities for characterization of today’s quantum materials, and developing the new, needed infrastructure for designing and synthesizing tomorrow’s quantum materials from the ground up, with quantum properties in mind.

About the speaker

Dr. Charles (Chuck) Black is a Senior Scientist and Director of the Center for Functional Nanomaterials, a national scientific user facility operated at Brookhaven National Laboratory for the U.S. Department of Energy.  Each year, the CFN supports the science of nearly 600 researchers from universities, industry, and national laboratories worldwide.

Prior to becoming Director, Dr. Black was Group Leader for CFN Electronic Nanomaterials, leading a research program exploring nanostructured materials for solar energy conversion.

From 1996 to 2006, Dr. Black was a Research Staff Member at the IBM Thomas J. Watson Research Center in Yorktown Heights, New York.  While at IBM he pioneered the use of polymer self-assembly as a high-resolution patterning materials for fabrication of semiconductor electronics. 

During his career, Dr. Black has also performed experimental research on ferroelectric non-volatile memories, nanocrystal-based electronic devices, superconductivity in metal nanoparticles, single-electron tunneling devices, and low-temperature scanning tunneling microscopy.

Dr. Black earned the Ph.D. degree in Physics from Harvard University in 1996, and B.S. degrees in Physics and Mathematics from Vanderbilt University in 1991.  Dr. Black has been a Member of the Board of Directors of the Materials Research Society (2015–17), is a Fellow of the American Physical Society, and is a Senior Member of the IEEE.

Add to calendar Add to Google Calendar
03/15/2019 - 5:00pm
 
 
17
18
19
20
21
22
23
 
Levon Pogosian - Simon Fraser University, Canada

Levon Pogosian - Simon Fraser University, Canada

Date: 
Mon, 03/18/2019 - 2:10pm
Location: 
Pupin Hall Theory Center, 8th Floor

 

"Cosmic microwaves and smoking guns"

Large scale B-mode patterns in CMB polarization, if detected, would constitute a “smoking gun” signature of primordial gravitational waves generated during an inflationary phase in the early universe. In this talk, I will discuss other sources of B-modes, such as primordial magnetic fields, axion-like fields and cosmic strings, and prospects of isolating their distinguishing features with future CMB measurements.

About the speaker

Levon Pogosian is a cosmologist, who considers the universe as a laboratory for testing the laws of Nature. His interests include dark energy and modified gravity, cosmic microwave background (CMB), structure formation, cosmic magnetic fields, cosmic strings and other topological defects and their implications for particle physics and cosmology.

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

Add to calendar Add to Google Calendar
03/18/2019 - 2:10pm
 
 
 
 
 
 
24
25
26
27
28
29
30
 
Sowjanya Gollapinni - University of Tennessee, Knoxville

Sowjanya Gollapinni - University of Tennessee, Knoxville

Date: 
Mon, 03/25/2019 - 12:30pm
Location: 
Pupin Hall Theory Center, 8th Floor

 

"Unlocking the Mysteries of Neutrinos with the Deep Underground Neutrino Experiment"

Neutrinos provide a promising window to probe a wide range of fundamental physics. Neutrino related discoveries in the last two decades indicate that the answer to the most sought after question of why we live in a matter-dominated universe maybe within reach. Although more than a trillion of neutrinos pass unnoticed through our bodies every second, they still remain largely mysterious. These ghostly little particles are notoriously difficult to detect given how rarely they interact with matter and require building immense and exquisitely sensitive detectors. The Deep Underground Neutrino Experiment (DUNE) is a long baseline neutrino oscillation experiment at Fermilab and South Dakota with primary goals of resolving the neutrino mass ordering and measuring the charge-parity violating phase, the indicator of a possible explanation for our matter dominated universe. However, the path to DUNE is technologically very challenging as it will be the biggest, most intense neutrino experiment ever to be built. After briefly reviewing the current state of neutrino physics, open questions and recent results from accelerator-based neutrino oscillation experiments, this talk will describe the DUNE experiment along with the rich physics that it offers and highlight some of the challenges involved in realizing such an experiment.

About the speaker

Sowjanya Gollapinni's research is focused on studying one of the fundamental particles in the Universe called neutrinos. In the world of subatomic physics, neutrinos form the most bizarre tiny entities known to date. Scientists study these elusive particles to understand the biggest puzzles in the universe, from the structure of the atom to the formation of a star.

Sowjanya is currently part of the MicroBooNE, Short-Baseline Near Detector (SBND) and Deep Underground Neutrino Experiment (DUNE) LArTPC experiment collaborations.

For a big picture understanding of the importance of neutrinos and Sowjanya is doing, you can watch her public lecture here.

Also, more details on Sowjanya's research can be found here.

Add to calendar Add to Google Calendar
03/25/2019 - 12:30pm
 
Bharat Ratra - Kansas State University

Bharat Ratra - Kansas State University

Date: 
Mon, 03/25/2019 - 2:10pm
Location: 
Pupin Hall Theory Center, 8th Floor

 

"Cosmological Seed Magnetic Field from Inflation"

A cosmological magnetic field of nG strength on Mpc length scales could be the seed magnetic field needed to explain observed few microG large-scale galactic magnetic fields. I first briefly review the observational and theoretical motivations for such a seed field, two galactic magnetic field amplification models, and some non-inflationary seed field generation scenarios. I then discuss an inflation magnetic field generation model. I conclude by mentioning possible extensions of this model as well as potentially observable consequences.

About the speaker

Bharat Ratra joined Kansas State University in 1996 as an assistant professor of physics. He was a postdoctoral fellow at Princeton University, the California Institute of Technology and the Massachusetts Institute of Technology. Ratra earned a doctorate in physics from Stanford University and a master's degree from the Indian Institute of Technology in New Delhi.

Currently, Bharat Ratra is a Distinguished Professor of Physics working in the areas of cosmology and astroparticle physics. He researches the structure and evolution of the universe. Two of his current principal interests are developing models for the large-scale matter and radiation distributions in the universe and testing these models by comparing predictions to observational data.

More details can be found here.

Add to calendar Add to Google Calendar
03/25/2019 - 2:10pm
 
Michael Coughlin - Caltech

Michael Coughlin - Caltech

Date: 
Tue, 03/26/2019 - 1:00pm
Location: 
705 Pupin Hall

 

"Before and after merger: Multi-messenger searches for compact binaries"

Binary neutron star mergers provide one of the richest laboratories for studying physics with ground-based interferometric gravitational-wave detectors such as advanced LIGO and Virgo. After such a merger, a compact remnant is left over whose nature depends primarily on the masses of the inspiralling objects and on the equation of state of nuclear matter. We will discuss the search for post-merger signals from GW170817. In addition, we will describe ongoing searches for the detection of transients likeGW170817 in electromagnetic wavelengths. With the Zwicky TransientFacility (ZTF) recently achieving first light, it is now fruitful to use its unprecedented combination of depth, field of view, and survey cadence to perform Target of Opportunity observations. We will demonstrate on short gamma-ray bursts how it is possible to use this system to do follow-up on this scale. Finally, we will discuss the ongoing efforts to use ZTF and a new instrument at the Kitt Peak 2.1m to find and characterize white dwarf binaries.

About the speaker

Michael Coughlin was an undergraduate at Carleton College, where he started in LIGO, performing detector characterization and unmodeled search related studies and also spent a summer doing seismic site analyses at Virgo. Afterwards, as a Churchill scholar at the Institute of Astronomy in Cambridge, he worked on parameter estimation of gravitational wave data, in particular compact binary coalescences. During graduate school at Harvard, he joined LSST, where he built and characterized a prototype calibration system for LSST, in addition to working with Pan-STARRS and ATLAS to search for gravitational-wave counterparts. He is now a prize post-doc at the California Institute of Technology, where he continues working on bridging the gap between gravitational-wave and observational astronomers with ZTF and KPED.

Add to calendar Add to Google Calendar
03/26/2019 - 1:00pm
 
 
 
Matthew Nichols - MIT

Matthew Nichols - MIT

Date: 
Fri, 03/29/2019 - 11:30am
Location: 
705 Pupin Hall

 

"Probing the 2D Fermi-Hubbard Model Under a Quantum Gas Microscope"

Ultracold fermionic atoms in optical lattices offer a pristine platform for quantum simulation of materials with strong electron correlations. With the advent of quantum gas microscopy, we now have the abilities to observe and manipulate these systems at the level of single atoms and lattice sites. In this talk, I will describe how we perform microscopy on fermionic 40K, and how we realize the two-dimensional Fermi-Hubbard model, a paradigm believed to capture the essence of high-Tc superconductivity in the cuprates. I will then discuss two experiments we performed using this system. In the first, we examined spatial spin and charge correlations in a fermionic Mott insulator. At half-filling, we observed antiferromagnetic spin correlations in the presence of doublon-hole bunching. Upon doping, these spin correlations weakened monotonically, and an interaction-enhanced Pauli hole emerged, a real-space manifestation of Pauli-blocking. In the second, we measured the spin conductivity of a homogeneous Mott insulator at half-filling, a quantity which is difficult to measure in the cuprates, and highly challenging to calculate theoretically. For strong interactions, we observed diffusive spin transport driven by super-exchange and doublon-hole assisted tunneling. Extending the technique developed for this measurement to finite doping could shed light on the complex interplay between spin and charge in the Hubbard model.

Add to calendar Add to Google Calendar
03/29/2019 - 11:30am
 
Peter Brown - Princeton University

Peter Brown - Princeton University

Date: 
Fri, 03/29/2019 - 5:00pm
Location: 
11M Conference Room, North West Corner
Nano Optics Seminar

Peter Brown

Princeton University

"Probing dynamical properties of Fermi-Hubbard systems with a quantum gas microscope"

The normal state of high-temperature superconductors exhibits anomalous transport and spectral properties that are poorly understood. Cold atoms in optical lattices have been used to realize the celebrated Fermi Hubbard model, widely believed to capture the essential physics of these materials. The recent development of fermionic quantum gas microscopes has enabled studying Hubbard systems with single-site resolution. Most studies have focused on probing equal-time spin and density correlations. In this talk, I will report on using a microscope to probe response functions associated with unequal-time correlations relevant for understanding the pseudogap and strange metal regimes of Fermi-Hubbard systems. First, I will describe the development of a technique to measure microscopic diffusion, and hence  resistivity, in doped Mott insulators. We have found that this resistivity exhibits a linear dependence on temperature and violates the Mott-Ioffe-Regel limit, two signatures of strange metallic behavior [1]. Next, I will report on the development of angle-resolved photoemission spectroscopy (ARPES) compatible with quantum gas microscopy and its application to studying pseudogap  physics in an attractive Hubbard system across the BEC-BCS crossover, setting the stage for future  studies of the pseudogap regime in repulsive Hubbard systems.

[1] P. T. Brown et al., "Bad metallic transport in a cold atom Fermi-Hubbard system" Science 363, 379-382 (2019).

Add to calendar Add to Google Calendar
03/29/2019 - 5:00pm
 
 
31
1
2
3
4
5
6
 
 
 
 
 
 
 
Add to Google Calendar