Role of electronic correlations in the kagome-lattice superconductor LaRh3B2

Abstract

${\mathrm{LaRh}}_{3}{\mathrm{B}}_{2}$ crystallizes in a layered structure where Rh atoms form a perfect kagome lattice. The material shows superconductivity at ${T}_{c}\ensuremath{\approx}2.6$ 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 we 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 ${\mathrm{LaRh}}_{3}{\mathrm{B}}_{2}$ and ${A\text{V}}_{3}{\mathrm{Sb}}_{5}$ ($A=\text{K,Cs,Rb}$). For ${\mathrm{LaRh}}_{3}{\mathrm{B}}_{2}$, it matches quantitatively with the observed ${T}_{c}$, supporting a conventional phonon-mediated pairing mechanism. By comparison to the $A{\mathrm{V}}_{3}{\mathrm{Sb}}_{5}$ family, we conjecture that there is a reduced importance of electron correlations in ${\mathrm{LaRh}}_{3}{\mathrm{B}}_{2}$.