William and Mary

Fall 2014

September 5, 2014 (Friday) 4:00-5:00p.m. Small Hall 110
Speaker: Dr. Predrag Nikolic, GMU
Host: Prof. Enrico Rossi
Title: The rise of topological quantum entanglement

Abstract: Entanglement is at the heart of quantum mechanics, the fundamental theory of our world. Yet, it is hardly ever seen in macroscopic collections of particles. We presently know of only one real system that is macroscopically entangled in a non-trivial way beyond any doubt. This is the two-dimensional electron gas in a magnetic field strong enough to produce fractional quantum Hall effect. Several other material families may also realize macroscopically entangled quantum states of strongly interacting electrons. This talk will be devoted to one such family, known as "topological insulators" (TIs), which recently became a world-wide research focus. More specifically, samarium hexaboride (SmB6) and its subfamily of Kondo (heavy fermion) insulators are the first promising candidates for strongly correlated TIs. I will present a neutron scattering experiment combined with field-theory calculations that indeed paint SmB6 as a correlated topological material. Then, I will discuss the rich physics of exotic symmetry breaking and electron fractionalization that one can anticipate in Kondo TIs. With some luck, these and similar materials may provide a new playground for exploring fundamental phenomena in nature, and perhaps even a new setting for topological quantum computation.

September 19, 2014 (Friday) 4:00-5:00p.m. Small Hall 110
Speaker: Carl Carlson, William & Mary
Host: Prof. E. Rossi
Title: The Proton Radius Puzzle
Abstract: The puzzle is easy to state: different ways of measuring the proton charge radius give different results, and the difference is seven standard deviations. Now four years after the discovery of this puzzle, the explanation is still not known. We will discuss how the measurements are made, and then will outline a selection of both ordinary and exotic proposals to explain the phenomenon.

September 26, 2014 (Friday) 4:00-5:00p.m. Small Hall 111

Speaker: Prof. Michael Kohl, Hampton University
Host: Prof. C. Perdrisat
Title: The proton radius puzzle - how can it be resolved?
Abstract:  The proton is not an elementary particle, it has a substructure governed by quarks and gluons. The spatial extensions of the electric charge and magnetization determine the size of the proton and its response to electromagnetic interaction. Recently, contradicting observations have challenged our understanding of the proton. The disagreement between proton radius determinations from high-precision muonic hydrogen spectroscopy and numerous atomic hydrogen and electron scattering measurements has become known as the proton radius puzzle, which has received much attention even in public media. The puzzle has a variety of possible resolutions, including physics beyond the Standard Model, missing conventional physics, and errors or underestimated uncertainties in the extraction of the radius from the data. I will discuss ways that will eventually help to resolve the puzzle.

October 3, 2014  (Friday) 4:00-5:00p.m. Small Hall 111

Speaker:  Prof. James Eckstein, University of Illinois-Urbana
Host: Prof. M. Qazilbash
Title: The Superconducting Proximity Effect 
Abstract: The superconducting proximity effect arises when a superconductor “shares” its pairs with a nonsuperconducting layer with which it is in good contact.  It has been studied in many experiments, sometimes showing unexpected behavior.  Renewed interest in proximity coupled superconductivity has arisen due to experimental results that suggest Majorana Fermions can form in devices that include topological materials, such as topological insulators and devices made from certain semiconductors such as InAs.  I will review superconductivity and the proximity effect, and then discuss some recent experiments in which proximity induced changes in normal state properties of both semiconductors and topological insulators have been measured.

October 10, 2014  (Friday) 4:00-5:00p.m. Small Hall 111
Speaker:  Julia M. Phillips, Sandia National Laboratory
Host: Prof. P. Vahle
Title: Research and Technologies for National Security: A perspective from a national security laboratory

Abstract: Sandia National Laboratories is the Nation’s largest national security laboratory. The mission of the laboratory to deliver engineered solutions for national security needs is built on a broad and deep base of scientific research and expertise. I will motivate the research at Sandia by describing the Laboratories’ historical evolution, research accomplishments and priorities, and current mission. I will then discuss some of the exciting research challenges that the Laboratories are pursuing, including topics such as Beyond Moore Computing, First to High Yield Fusion, Engineering of Materials Reliability, and Science & Engineering of Quantum Information Systems.

October 31, 2014 (Friday) 4:00-5:00p.m. Small Hall 111
Speaker: Prof. Luis Orozco, University of Maryland
Host:  Prof. S. Aubin

November 7, 2014 (Friday) 4:00-5:00p.m. Small Hall 111
Speaker: Gianpolo Carosi, LLNL
Host: Prof. A. Walker-Loud

November 14, 2014 (Friday) 4:00-5:00p.m. Small Hall 111
Speaker: Dr. Vincent Liu, University of Pittsburgh
Host: Prof. Enrico Rossi

November 21, 2014 (Friday) 4:00-5:00p.m. Small Hall 111
Speaker: Dr. Marcus Diefenthaler (University of Illinois - Urbana
Host: Prof. Wouter Deconinck

December 5, 2014 (Friday) 4:00-5:00p.m. Small Hall 111
Speaker: Raphael Busso, UC Berkeley
Host:  Prof. A. Walker-Loud