Past Events

Recently, superconductivity has been discovered for the electron gas formed at the interface of KTaO₃ with other oxides ^[1], T_c being almost an order of magnitude larger than what is seen for SrTiO₃.  The largest T_c is for <111> interfaces, with T_c 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 t_2g 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 T_c and how T_c 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.