Pair density wave order in multiband systems

TL;DR

This paper demonstrates how electron-density interactions in multiband systems can lead to pair density wave (PDW) superconductivity, with models showing PDW as a leading instability under certain attractive interactions.

Contribution

It reveals that finite-momentum pairing can arise from straightforward electron-density interactions in multiband systems, supported by mean-field analysis of specific models.

Findings

PDW order can become the leading instability with strong nearest-neighbour attraction.

Finite-momentum pairing is facilitated by nontrivial momentum-dependent form factors.

Transition from uniform to PDW superconductor can be understood via a quantum geometric argument.

Abstract

An indispensable ingredient for pair density wave (PDW) superconductivity is the presence of an attractive pairing interaction at finite momentum. Here, we show how this condition can be met with straightforward electron-density interactions in multiband systems. The electron-density interaction, when projected to the band basis, acquires form factors with nontrivial momentum dependence and thereby exhibits a potential tendency to a finite-momentum pairing instability. By applying a mean-field analysis to two simple multiband models, the checkerboard lattice and three-band Hubbard model, we find that PDW order can indeed become the leading instability if a strong nearest-neighbour attraction is present. Moreover, the condition for the transition from a uniform superconductor to a PDW superconductor is shown via a simple quantum geometric argument.