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Physics Colloquium: Dr. Kumar of Monmouth College Friday, October 11 at 4:00 pm in Currens 204

Oct 7, 2013

Speaker: Dr. Ashwani Kumar
Date: Friday, October 11, 2013
Time: 4 PM
Room: 205 Currens Hall

Superconductivity and Magnetism: Enemies Turned Allies


When some materials are cooled below a certain temperature, called the critical temperature (TC), they completely lose their electrical resistance and expel weak magnetic fields applied to them. These materials are called superconductors and this phenomenon is called superconductivity. Magnetic elds have long been known to suppress superconductivity through two main eects: rst, by raising the kinetic energy of the superconducting electrons (i.e., orbital de-pairing) and second, by aligning the electron spins (i.e., spin paramagnetic effect). However, we have observed pronounced enhancement in superconductivity upon application of a parallel magnetic field in two different two-dimensional (2D) superconducting systems: ultrathin homogeneously disordered amorphous Pb films and the 2D electron gas at the interface of LaAlO3 and SrTiO3 [Nature Phys. v7, pp.895 (2011)]. The focus of this presentation will be on amorphous lead (a-Pb) films where the TC enhancement as large as 13.5% in as high as 8T parallel field has been observed. Interestingly and contrary to recent predictions, the presence of paramagnetic impurities in the films diminished the field enhancement of superconductivity.

About the speaker:
Dr. Ashwani Kumar presently works as an assistant professor in the Department of Physics, Monmouth College. He received his M.Sc (with Honors) from Panjab University (India) in 1999 and his Ph.D. from Florida State University in 2009. His research interest is in quantum phase transitions (QPT) and superconductivity in geometrically constrained systems.

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