Physics CM/BIO/ECE Seminar Series Presents: Dr. Churna Bhandari

Wednesday, October 24, 2018 4:00pm

Physics Library, Room 223A, Physics Building


physics bldg

MU Physics & Astronomy Department’s Condensed Matter - Biological Physics - Electrical & Computer Engineering seminar series presents, "Spin-orbital entangled 2DEG at the polar LaAlO3 and non-polar iridates interface," presented by Dr. Churna Bhandari, University of Missouri, Wednesday, October 24, 4:00 p.m.

Dr. Bhandari writes, "The combination of a large spin-orbit coupling (SOC) and a reduced Coulomb interaction (U) in the 4d and 5d transition metal oxides has made these compounds hosts for a number of exotic quantum states, such as the spin-orbit driven Mott insulators, Weyl semimetals, axion insulators, and Kitaev spin liquids. In this talk, I would like to introduce 5d Sr2IrO4 /SrIrO3 (SIO214/113) iridates, an example of large SOC quasi-two-dimensional oxide material. The octahedral crystal field splits Ir (5d5) states into lower T2g and upper Eg states, where the six-fold degeneracy of the T2g states is further lifted by strong SOC effect resulting in the formation of spin-orbital entangled quartet Jeff= 3/2 (occupied) and doublet Jeff= 1/2 (half-filled). Because of the Coulomb interaction, the half-filled Jeff= 1/2 band splits into lower and upper Hubbard band forming a Mott-insulating (MI) state, which, if doped can lead interesting physics. Then, I will discuss an interface between the polar ordinary band insulator LaAlO3 (LAO) and non-polar SIO (214) or (113), which provides a way for electron doping in the SIO. Using density functional studies, we predict the formation of a novel spin-orbital entangled two-dimensional electron gas (2DEG) at the (001) interface between LAO and SIO (214) or (113), by the combined effect of the SOC, U, and polar catastrophe. Quite remarkably the 2DEG is found to be localized on a single IrO2 monolayer, unlike other polar interfaces such as LaAlO3/SrTiO3, where the 2DEG is several monolayers thick. The electron gas occupies the upper Jeff = 1/2 Hubbard band in the interface layer, which becomes half-filled with a simple square-like Fermi surface. If successfully grown, this would be the first candidate material to host the spin-orbital entangled 2DEG."

A pre-talk reception begins at 3:30 p.m. and refreshments will be served.