Enhancement of superconductivity by a parallel magnetic field in two-dimensional superconductors

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Date/Time:Thursday, 22 Mar 2012 - Thursday, 22 Mar 2012
Location:PHYSICS Room 5
Phone:515-294-5630
Channel:Condensed Matter Physics
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Ashwani Kumar
Monmouth College, Monmouth, IL

Magnetic fields have long been known to suppress superconductivity through two main effects: first, by raising the kinetic energy of the superconducting electrons (i.e., orbital depairing) 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: ultra thin homogeneously disordered amorphous Pb films and the 2D electron gas at the interface of LaAlO3 and SrTiO3 [Nature Phys. v7, pp895 (2011)]. The focus of this presentation will be 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.