Tuning electronic correlations in the Kagome metals $R{T}_3$B${}_2$

Abstract

The $R{T}_3$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.

11 pages, 9 figures, 1 table