Superconductivity and Electron Correlations in Kagome Metal LuOs3B2

Abstract

We report a comprehensive investigation of the physical properties of LuOs3B2, characterized by an ideal Os-based kagome lattice. Resistivity and magnetization measurements confirm the emergence of type-II bulk superconductivity with a critical temperature Tc=4.63 K. The specific heat jump and the calculated electron-phonon coupling parameter support a moderately coupled superconducting state. Electron correlation effects are supported by the enhanced Wilson ratios. First-principles calculations reveal hallmark features of kagome band structure, including Dirac points, van Hove singularities, and quasi-flat bands, primarily derived from the Os d orbitals. The inclusion of spin-orbit coupling opens a gap at the Dirac points, significantly altering the electronic properties. Furthermore, the superconductivity and electronic properties of isomorphic compounds are discussed. This work provides a thorough exploration of the superconducting and normal states of LuOs3B2, deepening the understanding of kagome superconductors.

Figures (6)

• Figure 1: (Color online) (a,b) Crystal structure of LuOs$_3$B$_2$, a side view, and a top view. (c) Rietveld refinement profile of LuOs$_3$B$_2$ polycrystalline sample.
• Figure 2: (Color online) (a) Temperature-dependent resistivity of LuOs$_3$B$_2$, with the inset illustrating the criteria for determining the onset of the resistivity drop. (b) Resistivity transition between 1.8 K and 5 K under applied magnetic fields ranging from 0 to 2 T. The horizontal dashed line at 50% of the normal-state resistivity defines the superconducting transition temperature under field. (c) Upper critical field $\mu_0 H_{c2}(T)$ as a function of temperature, fitted using the Ginzburg-Landau theory (red line). (d) Magnetoresistance measured at selected temperatures.
• Figure 3: (Color online) (a) Low-temperature susceptibility of LuOs$_3$B$_2$ in zero-field-cooled (ZFC, black) and field-cooled (FC, red) modes under a 10 Oe magnetic field. (b) Field-dependent initial magnetization at temperatures below $T_c$. (c) Temperature dependence of the lower critical field $H_{c1}(T)$. (d) Temperature dependence of magnetic susceptibility $\chi(T)$ at 1 T, with the red line indicating a Curie-Weiss fit.
• Figure 4: (Color online) (a) Temperature dependence of zero-field specific heat for LuOs$_3$B$_2$ from 300 K to 1.8 K. (b) Low-temperature specific heat data at 0 T and 3 T, plotted as $C_p/T$ versus $T$, with the solid line representing a fit to the 9 T data using the Debye model. (c) Normalized electronic specific heat $C_e / \gamma_n T_c$ after subtracting the normal state contribution. The solid red line presents a fit to the conventional BCS model.
• Figure 5: (Color online) First-principles electronic structure calculations of LuOs$_3$B$_2$.