Ferroelectricity-induced multiorbital odd-frequency superconductivity in SrTiO3

Abstract

We demonstrate that SrTiO3 can be a platform for observing the bulk odd-frequency superconducting state owing to its multiorbital/multiband nature. We consider a three-orbital tight-binding model for SrTiO3 in the vicinity of a ferroelectric critical point. Assuming an intraorbital spin-singlet s-wave superconducting order parameter, it is shown that the odd-frequency pair correlations are generated due to the intrinsic LS coupling which leads to local orbital mixing. Furthermore, we show the existence of additional odd-frequency pair correlations in the ferroelectric phase, which is induced by an odd-parity orbital hybridization term proportional to the ferroelectric order parameter. We also perform a group theoretical classification of the odd-frequency pair amplitudes based on the fermionic and space group symmetries of the system. The classification table enables us to predict the dominant components of the odd-frequency pair correlations based on the symmetry of the normal state Hamiltonian that we take into account. Furthermore, we show that experimental signatures of odd-parity orbital hybridization, which is an essential ingredient for ferroelectricity-induced odd-frequency pair correlations, can be observed in the spectral functions and density of states.

Source-reported materials — not catalogue approval

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