Dirac Dispersions and Fermi Surface Nesting in LaCuSb${}_2$

Abstract

LaCuSb${}_2$ is a superconductor with a transition temperature of about $T_{\text{c}}=0.9$K and is a potential platform where Dirac fermions can be experimentally observed. In this paper, we report systematic high-resolution studies of its electronic structure using the angle-resolved photoemission spectroscopy (ARPES) technique supported by the DFT calculation. The Fermi surface consists of four branches, of which the two inner ones are more 3-dimensional and the theoretical calculations reproduce well the experiment. We observe several linear dispersions forming Dirac-like structures. The nodal lines are present in the system along $\text{M}$-$\text{A}$ and $\text{X}$-$\text{R}$ and Dirac crossings along $\text{X}$-$\text{R}$ are observed by ARPES. Finally, the nesting between external Fermi surface pockets, which corresponds to charge density wave (CDW) modulation vector is enhanced in LaCuSb${}_2$ as compared to LaAgSb${}_2$, while CDW appears in the latter system.