Interplay between singlet and triplet pairings in multi-band two-dimensional oxide superconductors

• URL: http://arxiv.org/abs/2107.01100v2
• Date: Mon, 11 Oct 2021 17:00:42 GMT
• Title: Interplay between singlet and triplet pairings in multi-band two-dimensional oxide superconductors
• Authors: L. Lepori, D. Giuliano, A. Nava, and C. A. Perroni
• Abstract summary: We study the superconducting properties of multi-band two-dimensional transition metal oxide superconductors. The interplay between the singlet and the triplet pairings affects the dispersion of quasi-particle excitations in the Brillouin zone. Non-trivial topological superconducting states become stable as a function of the charge density.
• Score: 0.0
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: We theoretically study the superconducting properties of multi-band two-dimensional transition metal oxide superconductors by analyzing not only the role played by conventional singlet pairings, but also by the triplet order parameters, favored by the spin-orbit couplings present in these ma- terials. In particular, we focus on the two-dimensional electron gas at the (001) interface between LaAlO3 and SrTiO3 band insulators where the low electron densities and the sizeable spin-orbit couplings affect the superconducting features. Our theoretical study is based on an extended su- perconducting mean-field analysis of the typical multi-band tight-binding Hamiltonian, as well as on a parallel analysis of the effective electronic bands in the low-momentum limit, including static on-site and inter-site intra-band attractive potentials under applied magnetic fields. The presence of triplet pairings is able to strongly reduce the singlet order parameters which, as a result, are no longer a monotonic function of the charge density. The interplay between the singlet and the triplet pairings affects the dispersion of quasi-particle excitations in the Brillouin zone and also induces anisotropy in the superconducting behavior under the action of an in-plane and of an out- of-plane magnetic fields. Finally, non-trivial topological superconducting states become stable as a function of the charge density, as well as of the magnitude and of the orientation of the magnetic field. In addition to the chiral, time-reversal breaking, topological superconducting phase, favored by the linear Rashba couplings and by the on-site attractive potentials in the presence of an out- of-plane magnetic field, we find that a time-reversal invariant topological helical superconducting phase is promoted by not-linear spin-orbit couplings and by the inter-site attractive interactions in the absence of magnetic field.

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