Magnetic field-induced "mirage" gap in an Ising superconductor

TL;DR

This paper explores how an Ising superconductor's spectral properties are affected by magnetic fields and disorder, revealing 'mirage' gaps that indicate unique triplet pairing correlations.

Contribution

It introduces the concept of 'mirage' gaps in the spectrum of Ising superconductors under magnetic fields, highlighting their connection to equal-spin triplet pairing.

Findings

Mirage gaps appear at energies comparable to spin-orbit coupling strength.

Mirage gaps are signatures of equal-spin triplet pairing correlations.

Intervalley scattering affects the sensitivity of mirage gaps.

Abstract

Superconductivity is commonly destroyed by a magnetic field due to orbital or Zeeman-induced pair breaking. Surprisingly, the spin-valley locking in a two-dimensional superconductor with spin-orbit interaction makes the superconducting state resilient to large magnetic fields. We investigate the spectral properties of such an Ising superconductor in a magnetic field taking into account disorder. The interplay of the in-plane magnetic field and the Ising spin-orbit coupling leads to noncollinear effective fields. We find that the emerging singlet and triplet pairing correlations manifest themselves in the occurrence of "mirage" gaps: at (high) energies of the order of the spin-orbit coupling strength, a gap-like structure in the spectrum emerges that mirrors the main superconducting gap. We show that these mirage gaps are signatures of the equal-spin triplet finite-energy pairing correlations and due to their odd parity are sensitive to intervalley scattering.