[PAST EVENT] Christopher Triola: Physics Dissertation Defense

February 20, 2015
10am - 1pm
Small Hall, Room 122
300 Ukrop Way
Williamsburg, VA 23185Map this location
In this dissertation we study the electronic properties of certain two-dimensional chiral electron systems. We study the static and dynamic screening of gapped bilayer graphene and find important qualitative differences between the dielectric screening function obtained using a simplified 2-band model and that obtained using a more sophisticated 4-band model. We also formulate a continuum model to study the low-energy electronic properties of heterostructures formed by graphene on a strong three-dimensional topological insulator (TI) both for the case of commensurate and incommensurate stacking. We find that the proximity of the TI induces a strong enhancement of the spin-orbit coupling in graphene that can be tuned via the twist angle. Additionally, we examine the effect of a spin-active interface on the symmetry of proximity-induced superconducting pairing amplitudes in topological insulators. We compare our results to those for normal metals and ferromagnetic materials finding that the nontrivial spin chirality of the TI leads to qualitatively different behavior of the pairing amplitude. Lastly, we study the many-body instabilities of the Dirac states predicted to arise on the surfaces of topological Kondo insulators identifying regions of parameter space in which the system exhibits spin density wave, and charge density wave order.

Christopher Lawrence Charles Triola was born in Fredericksburg, Virginia in 1984. From a young age he knew he wanted to be a scientist but didn't find his passion for Physics until he went to college. He spent his first summer at William & Mary working with Marc Sher on the astrophysical consequences of neutrino-philic two-Higgs doublet models. This work was subsequently published in Physical Review D. The following year he took his first course on condensed matter physics to satisfy an elective and found it so interesting that he began working with his professor, Enrico Rossi, on the theoretical properties of chiral two-dimensional systems. In the summer of 2013 he traveled to Los Alamos, New Mexico for the waters. However, he was misinformed. Fortunately, that summer he began working with Alexander (Sasha) Balatsky at Los Alamos National Laboratory studying the effect of a spin-active interface on proximity-induced superconductivity in topological insulators. The next summer Christopher returned to Los Alamos to study the possibility of Coulomb-driven ordered states on the surfaces of topological Kondo insulators. During the Fall of 2014, Christopher was selected as a postdoctoral research fellow at the Nordic Institute for Theoretical Physics in Stockholm, Sweden, a position to start in March 2015. Thus, he has been given a few short months to prepare a dissertation and to defend it before he embarks on his first journey outside of his home country.