Fall 2017

Jean J. Heremans (Virginia Tech): Mesoscopic Spin- and Quantum Phase Coherence

Geometrical effects influencing the measured spin coherence and quantum phase coherence in mesoscopic structures were characterized by low-temperature spin-dependent quantum transport experiments.  The findings are of possible relevance for the design of devices for quantum technologies, and have foundational aspects as well.  The materials studied have strong spin-orbit interaction and are heterostructures of InSb, InAs, or InGaAs, and the semimetal Bi with its surface states. The materials were patterned into mesoscopic stadia, narrow channels or quantum interferometers, of typical size ~ 1 micron, comparable to the spin and quantum phase coherence lengths.  Aharonov-Bohm experiments, antilocalization, and universal conductance fluctuations were used to quantify the spin- and quantum phase coherence lengths.  Using geometrical constraints on the accumulation of quantum geometric phases, the work shows a correspondence, in a diffusive transport regime, between mesoscopic dephasing effects due to time-reversal symmetry breaking by magnetic fields, and spin decoherence due to spin-orbit interaction (Aharonov-Bohm / Aharonov-Casher correspondence).  The work also reveals device-geometrical influences on quantum phase coherence from coupling to the classical environment and geometrical effects of electron-electron interactions.

W. Vincent Liu Named a 2017 Fellow of the American Physical Society (APS)

  • By Leena Aggarwal
  • 16 October 2017

Congratulations to W. Vincent Liu for being named a 2017 Fellow of the American Physical Society (APS) by the Division of Atomic, Molecular & Optical Physics.

Vincent was elected for elucidating Landau damping of collective excitations in Bose-Einstein condensates, advancing the study of spin-polarized Fermi gases by introducing the concept of breached pair superfluidity, pioneering the theory of higher orbital bands in optical lattices, and working with experimentalists to confirm the theory.

 

Assistant Professor Tevis Jacobs Receives $305,000 from the National Science Foundation

  • By Leena Aggarwal
  • 16 October 2017

Tevis Jacobs, assistant professor of mechanical engineering and material science at the University of Pittsburgh's Swanson School of Engineering, received a grant from the National Science Foundation (NSF) to observe and measure nanoscale contact inside of an electron microscope-enabling for the first time visualization of the atomic structure of the component materials while they are in contact. The team's project will measure surface roughness of tiny particles and characterize the fundamental relationship between adhesion and roughness at small sizes.

Assistant Professor Benjamin Hunt wins DOE’s Early Career Award

  • By Leena Aggarwal
  • 16 October 2017

Benjamin Hunt, assistant professor of physics and member of the Quantum Electronics Group at Carnegie Mellon University was awarded a prestigious $750,000 Early Career Grant from the Department of Energy to study how layering different two-dimensional crystals (such as graphene and the magnetic insulator CrSiTe3) can lead to new, emergent properties in the composite layered structure.

Trapping of Polariton in Microcavities

  • By Leena Aggarwal
  • 9 October 2017

Bose-Einstein Condensation (BEC) is a process which occurs at low temperature when an ensemble of bosons cools down and enters a single quantum state. In most of the experiments, this condensation process includes the atomic gases. But in solid-state systems, which has a long history of generating new types of particles and quasiparticles, BEC can occur in quasiparticles e.g. fermion-like excitations of Bose- condensed Cooper pairs in a superconductor.

One class of such quasiparticles is polaritons, which form from electronic excitations coupled to photons in a microcavity. Polaritons are not fundamentally different in character from elementary particles; they are just highly renormalized to have different properties. In particular, polaritons can be viewed as photons having an effective mass and much stronger interactions than photons in a vacuum.

“A carefully engineered coupling between light and matter could pave the way to a room-temperature Bose–Einstein condensate.”

 

The Anne T. and Robert M. Bass Initiative on Innovation and Placemaking at the Brookings Institute

  • By Leena Aggarwal
  • 9 October 2017

The Anne T. and Robert M. Bass Initiative on Innovation and Placemaking is a collaboration between the Brookings Institution and Project for Public Spaces to support a city-driven and place-led world. According to a new report from the Brookings Institute, “Pittsburgh’s innovation economy is strong and growing, but city leaders can do more with its existing assets to compete globally and capitalize on the region’s growing innovation clusters”.

 “Through targeted research and analytics, strategic advising and recommendations, and communications guidance, Brooking aims to help position Pittsburgh as one of the top 30 most innovative cities in the world”.

Recently at the inaugural Brookings Centennial Scholar, Bruce Katz brings a different type of integrated problem-solving to the issues arising from global urbanization and the challenges of a city-driven century. Bruce Katz Capturing the Next Economy: Pittsburgh’s rise as a global innovation city”.

 

U.S. Army Research Laboratory Open Campus Open House

Speaker(s): 
Various
Dates: 
Wednesday, October 18, 2017 - 9:00am to Thursday, October 19, 2017 - 5:00pm

The U.S. Army Research Laboratory will hold its fourth Open Campus Open House. This year we ask, "Who is the nation’s premier laboratory for land forces focused on discovery and innovation for the Army of 2035 and beyond?" The U.S. Army Research Laboratory is interested in working with you. 

Towards a Realist View of Quantum Field Theory

Speaker(s): 
James Fraser, Center Postdoc Fellow
Dates: 
Friday, October 6, 2017 - 12:00pm

Can a scientific realist epistemology be maintained in the context of quantum field theory? I have suggested, following similar proposals by David Wallace and Porter Williams, that the best hope for the realist is to be found in the effective field theory approach. After explaining the key motivations for this view I focus here on two anti-realist replies: the first suggesting that it falls foul of familiar pessimistic induction style arguments and the second that it fails to clearly distinguish itself from constructive empiricism. While I don’t think these objections are fatal they do...

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