Optical response and electron energy loss spectra of boron arsenide using linear response theory.

Abstract

In this study, we present optical and electron energy loss spectra of BAs using linear response time-dependent density functional theory. The spectra show the effects of local field and electron-hole interactions. The excitonic effects are included by considering the long-range-corrected and bootstrap exchange-correlation kernels. When the optical spectra from the long-range corrected and bootstrap kernels are compared with those from random phase approximation and adiabatic local density approximation, clear signatures of electron-hole interactions are observed. The current study marks the presence of continuum excitonic effects. The exciton binding energies of 38 and 44 meV deduced from long-range-corrected and bootstrap kernels using the hydrogenic model, respectively, are very close to the data obtained from GW-Bethe-Salpeter equation. It is found that the local-field effects reduce whereas electron-hole interactions enhance the high-frequency dielectric constant. Moreover, a clear modification in the electron energy loss spectra is visible after incorporating the local-field effect. We discuss the effect of the material-dependent parameter <i>α</i>, deduced from a number of approaches, on both optical and electron energy loss spectra. This study corroborates the effectiveness of long-range-corrected kernel in exploring the optical and electronic spectra when <i>α</i> evaluated using the scheme developed by the authors is considered.