First-principle study of the electronic structure of layered CuSe.

Copper selenide (CuSe) has attracted significant attention due to the extensive applications in thermoelectric and optoelectronic devices over the last few decades. Among various phase structures of CuSe, layered CuSe exhibits unique properties, such as purely thermal phase transition, high carrier mobility, high optical absorbance and high photoconductivity. Herein, we carry out a systematic investigation for the electronic structures of layered CuSe with several exchange-correlation functionals at different levels through first-principle calculations. It can be found that the electronic structures of layered CuSe are highly sensitive to the choice of functionals, and the correction of on-site Coulomb interaction also has a noticeable influence. Comparing with the results calculated with hybrid functional and GWmethod, it is found that the electronic structures calculated with LDA +functional are relatively accurate for layered CuSe. In addition, the in-plane biaxial strain can lead to the transition of electronic properties from metal to semiconductor in the layered CuSe, attributed to the change of atomic orbital hybridization. Furthermore, we explore the spin-orbit coupling (SOC) effect of CuSe and find that the weak SOC effect on electronic structures mainly results from spatial inversion symmetry of CuSe. These findings provide valuable insights for further investigation on this compound.