Substantial optical dielectric enhancement by volume compression in LiAsSe${}_2$

Based on first-principles calculations, we predict a substantial increase in the optical dielectric function of LiAsSe${}_2$ under pressure. We find that the optical dielectric constant is enhanced threefold under volume compression. This enhancement is mainly due to the dimerization strength reduction of the one-dimensional (1D) As–Se chains in LiAsSe${}_2$, which significantly alters the wavefunction phase mismatch between two neighboring chains and changes the transition intensity. By developing a tight-binding model of the interacting 1D chains, the essential features of the low-energy electronic structure of LiAsSe${}_2$ are captured. Our findings are important for understanding the fundamental physics of LiAsSe${}_2$ and provide a feasible way to enhance the material optical response that can be applied to light harvesting for energy applications.