Role of electronic correlations in the Kagome lattice superconductor LaRh$_3$B$_2$

TL;DR

This study investigates LaRh$_3$B$_2$, a Kagome lattice superconductor, revealing that its superconductivity is likely phonon-mediated with minimal influence from electronic correlations, supported by experimental and first-principles calculations.

Contribution

It provides a comprehensive analysis combining experiments and first-principles calculations to understand the superconductivity and electronic structure of LaRh$_3$B$_2$, highlighting the role of Kagome bands and electron-phonon interactions.

Findings

Superconductivity at $T_c \\approx 2.6$~K without density wave signatures.

Kagome bands include flat bands, Dirac cones, and van Hove singularities.

Electron-phonon coupling explains the observed $T_c$, indicating conventional pairing.

Abstract

LaRh$_3$B$_2$ crystallizes in a layered structure where Rh atoms form a perfect Kagome lattice. The material shows superconductivity at $T_c \approx 2.6$~K\@ and no signature for density wave instabilities. We report our measurements of electronic transport, magnetization, and heat capacity in the normal and superconducting state, and derive normal and superconducting parameters. From first principles calculations of the electronic band structure, we identify all features of Kagome bands predominantly formed by the Rh $d$ orbitals: a flat band, Dirac cones, and van Hove singularities. The calculation of the phonon dispersions and electron-phonon coupling suggests a strong similarity between LaRh$_3$B$_2$ and AV$_3$Sb$_5$ (A=K,Cs,Rb). For LaRh$_3$B$_2$, it matches quantitatively with the observed $T_c$, supporting a conventional phonon mediated pairing mechanism. By comparison to the $A$V$_3$Sb$_5$ family, we conjecture a reduced importance of electron correlations in LaRh$_3$B$_2$.