Some new findings in superconductivity in SrTiO3 and KTaO3
Anand Bhattacharya, Argonne National Laboratory
The perovskite oxides SrTiO3 (STO) and KTaO3 (KTO) are both wide-bandgap perovskite insulators, on the verge of ferroelectricity. While STO can be doped readily into a metallic state, KTO is harder to dope in the bulk. Lightly doped STO is in fact a superconductor, with the earliest example of a 'dome' in the doping vs Tc phase diagram. I will present some recent results, where we show that bulk STO is in fact superconducting at carrier densities far below previously thought, in a regime deep in the anti-adiabatic limit, though the superconductivity is inhomogeneous. In the second half of this talk, I shall discuss our recent discovery of superconductivity in 2-DEGs formed at (111) oriented interfaces of KTO. Here we find transition temperatures as high as 2.2 K, approximately an order of magnitude higher than in the very heavily studied 2DEGs formed at LaAlO3/SrTiO3 interfaces. Furthermore, in some of our 2DEGs we find that the superconductivity to be highly anisotropic, forming a 'stripe' like phase. I will try to explain what our findings might mean in light of our current understanding of superconductivity in this class of materials.
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C. Liu et al., arXiv: 2004.07416