Electronic and magnetic properties of LaCu$_{x}$Sb$_{2}$ tuned by Cu occupancy

TL;DR

This study investigates how varying Cu occupancy in LaCu$_{x}$Sb$_{2}$ affects its electronic, magnetic, and superconducting properties, revealing systematic changes in Fermi surface and quantum oscillations linked to composition.

Contribution

It provides a detailed analysis of the dependence of physical properties on Cu-site occupancy and combines experimental measurements with DFT calculations to elucidate electronic structure changes.

Findings

Residual resistivity ratio varies with Cu occupancy

Quantum oscillations depend on Cu content and reveal Fermi surface changes

Electronic structure calculations agree with experimental Fermi surface observations

Abstract

We report thermodynamic and transport properties of LaCu$_{x}$Sb$_{2}$ ($0.92 \leq x \leq 1.12$), synthesized by controlling the initial loading composition and investigated by magnetization, electrical resistivity, and specific heat measurements. The physical properties of this system are highly dependent on Cu-site occupancy $x$, where residual resistivity ratio (RRR), magnetoresistance (MR), superconducting transition temperature ($T_{c}$), and electronic specific heat coefficient ($\gamma$) indicate a systematic variation as a function of $x$. The Shubnikov-de Haas quantum oscillations are observed in magnetoresistance measurements for samples close to the Cu stoichiometry $x \sim 1$, while the de Haas-van Alphen oscillations are detected in a wide range of $x$ ($0.92 \leq x \le 1.12$). For $H \parallel c$, the oscillation frequency indicates a clear $x$-dependence, implying a systematic change of Fermi surface. DFT calculations for the sample closest to ideal Cu stoichiometry reveal electronic structures with a common feature of the square-net-based semimetals, which is in good agreement with the experimental observations. The magnetic response of LaCu$_{x}$Sb$_{2}$ to magnetic fields is anisotropic owing to the Fermi surface anisotropy. Our results show how the physical properties are influenced by the Cu-site occupancy $x$, linked to the electronic bands arising from the Sb square net.