Nature of the electron-phonon coupling in KTaO3*

The discovery of superconductivity in KTaO3 heterostructures, with critical temperatures an order of magnitude higher than that of SrTiO3 heterostructures, has spurred significant interest in the last couple of years. The relevance of the polar modes for pairing, as well as the role of spin-orbit coupling are still under debate. Here, we present our findings on the Rashba-like coupling between conduction electrons and soft transverse polar modes. Combining ab initio computations and a microscopic model involving spin-orbit coupled t2g electrons, we find a significant electron-phonon coupling to the ferroelectric mode in KTaO3 and SrTiO3. We compare both systems and discuss the implications for the origin of superconductivity in bulk and heterostructures.