Electronic correlations in the normal state of kagome superconductor KV$_3$Sb$_5$

TL;DR

This study uses advanced theoretical methods to analyze the electronic correlations and magnetic properties of KV$_3$Sb$_5$, revealing weak local correlations, nodal lines with Berry phases, and implications for superconductivity.

Contribution

It provides the first detailed theoretical investigation of the correlated electronic structure and magnetic properties of KV$_3$Sb$_5$ using DFT+DMFT methods.

Findings

KV$_3$Sb$_5$ are good metals with weak local correlations.

The materials exhibit Pauli-like paramagnetism and no local moments.

Band crossings form nodal lines with quantized Berry phases.

Abstract

Recently, intensive studies have revealed fascinating physics, such as charge density wave and superconducting states, in the newly synthesized kagome-lattice materials $A$V$_3$Sb$_5$ ($A$=K, Rb, Cs). Despite the rapid progress, fundamental aspects like the magnetic properties and electronic correlations in these materials have not been clearly understood yet. Here, based on the density functional theory plus the single-site dynamical mean-field theory calculations, we investigate the correlated electronic structure and the magnetic properties of the KV$_3$Sb$_5$ family materials in the normal state. We show that these materials are good metals with weak local correlations. The obtained Pauli-like paramagnetism and the absence of local moments are consistent with recent experiment. We reveal that the band crossings around the Fermi level form three groups of nodal lines protected by the spacetime inversion symmetry, each carrying a quantized $\pi$ Berry phase. Our result suggests that the local correlation strength in these materials appears to be too weak to generate unconventional superconductivity, and non-local electronic correlation might be crucial in this kagome system.