physics & astronomy

Colloquium: Topological Surface States in Topological Insulators, Superconductors and Beyond

Topological Surface States in Topological Insulators, Superconductors and Beyond

M Zahid Hasan, Dept of Physics, Princeton University

Bulk Topological Insulators are a new phase of electronic matter which realizes a non-quantum-Hall-like topological state in the bulk matter and unlike the quantum Hall liquids can be turned into superconductors. In this talk, I will first review the basic theory of topological matter and experimental probes that reveal topological order. I will discuss experimental results that demonstrate the fundamental properties of topological insulators such as spin-momentum locking, non-trivial Berry’s phases, mirror Chern number, absence of backscattering or no U-turn rule, protection by time-reversal symmetry and the existence of room temperature topological order (at the level of M.Z.H and C.L. Kane, Rev. of Mod. Phys., 82, 3045 (2010)). I will then discuss the possible exotic roles of broken symmetry phases such as superconductivity and magnetism in doped topological insulators and their potential device applications in connection to our recent results as well as outline the emerging research frontiers of the field as a whole. Time permitting, I will also present experimental results on a new class of topological insulators beyond the Kane-Mele Z2 theory.

Observation of the thermal Casimir effect and new limits on non-Newtonian forces in the micrometer range

Quantum theory predicts the existence of the Casimir force between macroscopic bodies, a force arising from the zero-point energy of electromagnetic field modes around them. I will report the experimental observation of the thermal Casimir force between two gold plates, due to thermal rather than quantum fluctuations of the electromagnetic field at room-temperature. The thermal Casimir force dominates over the quantum force for separations greater than a micrometer. We use our measurements to place new upper bounds on short-range exotic forces, arising, for example, in quantum gravity theories with extra dimensions.

Colloquium: Discovery of a North-South Asymmetry in the Distribution of Local Stars and its Implications

Studies which would try to fix the local dark matter density through observations of the nearby stars invariably assume that the stars are in gravitational equilibrium. In recent years, however, it has become clear that the Milky Way displays many transient phenomena; it is a much more violent place than earlier thought. I will show how observations of the local solar neighborhood from the Sloan Digitial Sky Survey can probe the vertical equilibrium of the Galactic disk, by testing the symmetries present in the stars' distribution. Our analysis reveals a failure of north-south symmetry with respect to the galactic plane and thus that vertical equilibrium is wanting. I will consider our result in light of other observational studies, suggest further observational tests, and finally offer a perspective on its implications for dark-matter direct detection experiments.

UK Physics Professor Discovers Important Experimental Result

University of Kentucky physics Professor Tim Gorringe's research collaboration has recently gained attention for an important experimental result.

Cosmos and Computers: Gary Ferland discusses infrastructure upgrades for studying space.

The University of Kentucky recently announced big upgrades to its supercomputing infrastructure. This means more power for researchers across the campus working on some of the questions that have puzzled us the longest. 

One such researcher is Professor Gary Ferland of the Department of Physics and Astronomy. Since the late 1970s, he’s been using computer modeling software to carry out experiments that would otherwise be impossible. With his widely used program Cloudy which simulates clouds of interstellar matter out in space and UK’s high-tech supercomputing infrastructure, Ferland and his students have been able to help answer some of the biggest questions facing astronomers as well as society.
 

This podcast was produced by Patrick O'Dowd.

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This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

A New Path Forward: UK Proposes to Self-fund Transformation of Campus

University of Kentucky President Eli Capilouto Thursday praised the partnership of Gov. Steve Beshear and legislative leaders who are strongly supporting UK's self-financing of a dramatic $275 million transformation of the campus, including a new Academic Sciences building.

Colloquium: Viscosity, Quark Gluon Plasma, and String Theory

Viscosity, quark gluon plasma, and string theory

Viscosity is a very old concept which was introduced to physics by Navier in the 19th century. However, in strongly coupled systems, viscosity is difficult to compute from first principle. In this talk I will describe some recent surprising developments in string theory which allow one to compute the viscosity for a class of strongly interacting quantum fluids not too dissimilar to the quark gluon plasma. I will describe efforts to measure the viscosity and other physical properties of the quark gluon plasma created in relativistic heavy ion collisions.

Cosmic Linear Accelerators: Extreme Reconnection and other Surprises from the Crab Nebula

The unexpected discovery of gamma-ray flares from the Crab Nebula may have surprising implications for plasma astrophysics. Standard particle acceleration mechanisms cannot account for the energies of the flaring photons. Instead, these observations point toward an acceleration process involving rapid destruction of magnetic field through reconnection. I will discuss the extreme particle acceleration process that may lead to the flares, and the likely role of current-driven instabilities in triggering reconnection in the Crab and elsewhere.

Colloquium: Glimpsing Color in the World of Black and White

Glimpsing color in a world of black and white

Protons, neutrons and all the many other strongly interacting subnuclear particles, known as hadrons, are made of quarks and gluons. These fundamental constituents are held together by a color force described by quantum chromodynamics (QCD). A detailed understanding of how the strong coupling regime of QCD, which is responsible for confinement and dynamical chiral symmetry breaking, determines the spectrum and structure of hadrons will be outlined. Such studies, both experimental and theoretical, color in the picture of strong dynamics. What we know now and the glimpses to come from accelerator facilities like that at Jefferson Lab will be described.

New Faculty 2012: Meet Dale Kocevski

The Department of Physics & Astronomy is excited to welcome professor Dale Kocevski to its faculty!

Professor Kocevski joins us this fall focused on researching distant galaxies that host actively accreting supermassive black holes. Evidence suggests that the evolution of galaxies is intricately linked to the presence of black holes at their center. Kocevski plans to use multi-wavelength observations to examine the demographics of the galaxies that host these growing black holes.  
 
This podcast is part of a series highlighting the new faculty members who joined the College of Arts and Sciences in the fall 2012 semester.
 

This podcast was produced by Patrick O'Dowd.

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This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

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