NBIA/QDev Condensed Matter Seminar by Aleander Balatsky – University of Copenhagen

NBIA/QDev Condensed Matter Seminar by Aleander Balatsky

Two-band superconductivity in doped SrTiO3 films and interfaces

We examine the possibility of multi-band superconductivity in SrTiO3 interfaces by investigating the effects of a two-dimensional two-band model. In undoped SrTiO3, one of the bands is occupied, while the upper band is empty. As the chemical potential shifts, due to doping by negative charge carriers or application of an electric field, the second band becomes occupied, giving rise to a strong enhancement of the transition temperature and a sharp feature in the gap functions, which is manifested in the local density of states spectrum. By comparing our results with tunneling experiments in Nb-doped SrTiO3, we find that intra-band pairing dominates over inter-band pairing, unlike other known multi-band superconductors. Given the similar transition temperature and band structure of LaAlO3/SrTiO3 heterostructures, we speculate that the superconductivity observed in SrTiO3interfaces may be similar in nature to that of bulk SrTiO3, involving multiple bands with distinct electronic occupations.