Abstract
Recently, superconductivity has been discovered for the electron gas formed at the interface of KTaO3 with other oxides [1], Tc being almost an order of magnitude larger than what is seen for SrTiO3. The largest Tc is for <111> interfaces, with Tc for <110> interfaces about half of this, and that for <001> interfaces either extremely small or non-existent. This points to the role of orbital degeneracy, the degeneracy of t2g states being maximal for <111>, and completely lifted for <001> due to interface confinement. A theory that encompasses this effect is pairing via the transverse optic mode that leads to ferroelectricity in related perovskites, as to linear order this involves inter-orbital interactions (which in turn gives rise to a large Rashba effect that is strongly sensitive to orientation). In this talk, I will compare this theory to relevant data for KTaO3, in particular the doping dependence of Tc and how Tc and thermodynamic and transport properties vary with interface orientation [2].
[1]. C. Liu et al, Science 371, 716 (2021).
[2]. C. Liu et al, arXiv:2203.05867.
Anyone interested is welcome to attend.