Interband pairing as the origin of the sublattice dichotomy in monolayer FeSe/SrTiO_3

TL;DR

This paper proposes that interband pairing explains the sublattice dichotomy observed in monolayer FeSe/SrTiO3, highlighting its essential role in the material's superconductivity regardless of symmetry-breaking origin.

Contribution

It introduces the idea that interband pairing is the fundamental cause of sublattice dichotomy, applicable whether symmetry breaking occurs in the normal or pairing state.

Findings

Interband pairing explains the sublattice dichotomy in spectra.

Sublattice polarization of Fermi surfaces supports interband pairing.

Interband pairing is crucial for understanding superconductivity in the material.

Abstract

Sublattice dichotomy in monolayer FeSe/SrTiO$_3$, signaling the breaking of symmetries exchanging the two Fe sublattices, has recently been reported. We propose that interband pairing serves as the origin of this dichotomy, regardless of whether the symmetry is broken in the normal state or in the pairing state. If symmetry breaking occurs in the normal state, the Fermi surfaces are sublattice-polarized, and the intersublattice d-wave pairing naturally acts as interband pairing, reproducing the observed dichotomy in the spectra. Alternatively, if symmetry breaking takes place in the pairing state, it manifests as the coexistence of intraband and interband pairing, with the constraint that interband pairings share the same sign while intraband pairings carry opposite signs. In both cases, interband pairing is indispensable, establishing it as a key ingredient for understanding superconductivity in monolayer FeSe/SrTiO$_3$.