Phonon-mediated superconductivity in the Sb-square-net compound LaCuSb${}_2$

We investigated the electronic structure and superconducting properties of single-crystalline LaCuSb${}_2$. The resistivity, magnetization, and specific heat measurements showed that LaCuSb${}_2$ is a bulk superconductor. The observed Shubnikov-de Haas oscillation and magnetic field dependence of the Hall resistivity can be reasonably understood assuming a slightly hole-doped Fermi surface. Electron-phonon coupling calculation clarified the difference from the isostructural compound LaAgSb${}_2$ indicating that (i) low-frequency vibration modes related to the interstitial layer sandwiched between the Sb-square nets significantly contribute to the superconductivity and (ii) carriers with sizable electron–phonon coupling distribute isotropically on the Fermi surface. These are assumed to be the origin of higher superconducting transition temperature compared with LaAgSb${}_2$. We conclude that the superconducting properties of LaCuSb${}_2$ can be understood within the framework of conventional phonon-mediated mechanism.