Tuning electronic correlations in the Kagome metals $RT_3$B$_2$

TL;DR

This study investigates the electronic structure, superconductivity, and correlations in Kagome lattice materials $RT_3$B$_2$, highlighting differences between LuOs$_3$B$_2$ and YCo$_3$B$_2$ related to their electronic and lattice properties.

Contribution

It provides a comparative analysis of two Kagome metals, revealing how composition influences electronic correlations, superconductivity, and lattice dynamics.

Findings

LuOs$_3$B$_2$ is superconducting with $T_c=4.75$K.

YCo$_3$B$_2$ remains non-superconducting above 1.8K.

Both materials show Kagome-derived electronic features.

Abstract

The $RT_3$B$_2$ ($R=$Y, Lu, $T=$ Co, Os) family hosts a perfect kagome lattice of $T$ atoms, offering an interesting platform to investigate the interplay of electronic structure, superconductivity, and lattice dynamics. Here, we compare two members of this family, LuOs$_3$B$_2$ and YCo$_3$B$_2$, with similar crystallography but differing chemical composition, leading to distinct electronic correlation strengths and spin-orbit coupling effects. We confirm superconductivity in LuOs$_3$B$_2$ with $T_c = 4.75$K, while YCo$_3$B$_2$ remains non-superconducting above 1.8K. First-principles estimates of the electron-phonon coupling for LuOs$_3$B$_2$ are consistent with its observed $T_c$ and suggest a moderate coupling strength. Both materials exhibit kagome-derived electronic features, including quasi-flat bands, Dirac cones, and van Hove singularities. Fermi surface calculations reveal quasi-one-dimensional behavior along the $c$-axis in YCo$_3$B$_2$, in contrast to the more three-dimensional Fermiology of LuOs$_3$B$_2$. Phonon calculations for LuOs$_3$B$_2$ show imaginary modes, indicating potential lattice instabilities. Experimental estimates of the Wilson and Kadowaki-Woods ratios point to non-negligible electronic correlations in both compounds.