Pair density modulation from glide symmetry breaking and nematic superconductivity

TL;DR

This paper introduces a microscopic model explaining pair density modulation in iron-based superconductors through glide symmetry breaking and nematic superconductivity, revealing sublattice textures and gap anisotropies.

Contribution

It proposes a novel explanation for pair density modulation involving glide symmetry breaking and nematic pairing, linking lattice symmetry to superconducting gap structure.

Findings

Sublattice texture on the Fermi surface causes gap modulation.

Distinct gap maxima and minima on inequivalent iron sublattices.

Insights into pairing symmetry and phase transitions from modulations.

Abstract

Pair density modulation is a superconducting state, recently observed in exfoliated iron-based superconductor flakes, in which the superconducting gap oscillates strongly with the same periodicity as the underlying crystalline lattice. We propose a microscopic model that explains this modulation through a combination of glide-mirror symmetry breaking and the emergence of nematic superconductivity. The first ingredient results in a sublattice texture on the Fermi surface, which is aligned with the anisotropic superconducting gap of the nematic $s_\pm+d$ state. This gives rise to distinctive gap maxima and minima located on the two inequivalent iron sublattices while still being a zero-momentum pairing state. We discuss how further investigation of such modulations can give insight into the nature of the superconducting pairing, such as the signs of the order parameters and visualization of a phase transition to a mixed two-component state using local probes.