Description:

Professor Venkat Chandrasekhar, Northwestern University 

Title: Superconductivity, Magnetism, Anisotropy, Spin-Orbit Interactions and Memory: The Remarkable Properties of the Conducting Gas at (111) SrTiO3 Based Interfaces

Abstract: The 2D conducting gas that forms at the interface between the two insulators LaAlO3 (LAO) and SrTiO3 (STO) has garnered a lot of attention due to wide variety of physical phenomena that it exhibits, including strong spin–orbit coupling, superconductivity, magnetism, and localization effects, among others. Most of the experimental and theoretical work so far has been on LAO/STO interfaces grown in the (001) crystal orientation, in which the system has rectangular symmetry at the interface. More recently, interest has focused on LAO/STO interface grown in the (111) crystal orientation, in which the interface has hexagonal symmetry, similar to graphene and transition-metal-dichalcogenides, raising the possibility of topological effects. As with the (001) interface structures, we find that the system exhibits both superconductivity and magnetism coexisting at the same interface. Unlike the (001) interface, the (111) interface is highly anisotropic, showing different characteristics along different crystal directions in all its properties, including longitudinal resistivity, Hall effect, quantum capacitance, superconductivity and magnetism. The anisotropy is a signature of an electronic nematic state that onsets below ~20 K. We observe an unusual memory effect in the superconducting state: the system remembers the gate voltage at which it is cooled through the superconducting transition. I will also discuss more recent results on (111) LSAT/STO heterostructures that indicate magnetism whose origin lies in a gate-tunable spin-orbit interaction.

Host: Jim Sauls