Interplay between Pair Density Wave and a Nested Fermi Surface

TL;DR

This paper explores how pair density wave order interacting with nested Fermi surfaces can lead to spontaneous time-reversal symmetry breaking and complex electronic states, with implications for materials like CsV3Sb5.

Contribution

It demonstrates that nesting-induced pair density wave states can naturally break time-reversal symmetry and produce stable Bogoliubov Fermi pockets, advancing understanding of unconventional superconductivity.

Findings

TRS breaking arises from PDW and FS nesting interplay.

Stable Bogoliubov Fermi pockets are identified.

Predicted charge density wave orders from PDW melting.

Abstract

We show that spontaneous time-reversal-symmetry (TRS) breaking can naturally arise from the interplay between pair density wave (PDW) ordering at multiple momenta and nesting of Fermi surfaces (FS). Concretely, we consider pair-density-wave superconductivity on a hexagonal lattice with nested FS at $3/4$ electron filling, which is related to a recently discovered superconductor CsV$_3$Sb$_5$. Because of nesting of the FS, each momentum $\bk$ on the FS has at least two counterparts $-\bk\pm\mathbf{Q}_{\alpha}$ ($\alpha=1,2,3$) on the FS to form finite momentum ($\pm\mathbf{Q}_{\alpha}$) Cooper pairs, resulting in a TRS and inversion broken PDW state with stable Bogoliubov Fermi pockets. Various spectra, including (local) density of states, electron spectral function and the effect of quasi-particle interference, have been investigated. The partial melting of the PDW will give rise to $4\times{}4$ and $\frac{4}{\sqrt{3}}\times\frac{4}{\sqrt{3}}$ CDW orders, in addition to the $2\times2$ CDW. Possible implications to real materials such as CsV$_3$Sb$_5$ and future experiments have been further discussed.