Mechanism of exotic density-wave and beyond-Migdal unconventional superconductivity in kagome metal AV3Sb5 (A=K, Rb, Cs)

TL;DR

This paper explains the emergence of exotic density waves and unconventional superconductivity in kagome metal AV3Sb5 through a paramagnon interference mechanism, revealing new pairing states and their coexistence.

Contribution

It introduces a novel interference mechanism explaining density-wave formation and predicts the coexistence of singlet and triplet pairing states in kagome metals.

Findings

Bond-density-wave caused by paramagnon interference.

Prediction of both s-wave and p-wave superconducting states.

Discussion of similarities with Fe-based superconductors.

Abstract

Exotic quantum phase transitions in metals, such as the nematic and smectic states, were discovered one after another and found to be universal now. The emergence of unconventional density-wave order in frustrated kagome metal AV$_3$Sb$_5$ and its interplay with exotic superconductivity attract increasing attention. We reveal that the smectic bond-density-wave is naturally caused by the paramagnon interference mechanism, because strong scatterings among different van-Hove singularity points are induced. In addition, the fluctuations of the bond-order induce sizable "beyond-Migdal" pairing glue, and therefore both singlet nodal $s$-wave pairing and triplet $p$-wave pairing states are expected to emerge. The coexistence of both states would explain exotic superconducting states. Unexpected similarities between kagome metal and some Fe-based superconductors are discussed. This study enables us to understand the exotic density wave, superconductivity and their interplay in kagome metals based on the interference mechanism.