1204.2724 (S. Sharma et al.)

Enhanced excitonic effects in the energy loss spectra of LiF and Ar at
large momentum transfer    [PDF]

S. Sharma, J. K. Dewhurst, A. Sanna, A Rubio, E. K. U. Gross

It is demonstrated that the bootstrap kernel [\onlinecite{sharma11}] for finite values of ${\bf q}$ crucially depends upon the matrix character of the kernel and gives results of the same good quality as in the ${\bf q} \rightarrow 0$ limit. The bootstrap kernel is further used to study the electron loss as well as absorption spectra for Si, LiF and Ar for various values of ${\bf q}$. The results show that the excitonic effects in LiF and Ar are enhanced for values of ${\bf q}$ away from the $\Gamma$-point. The reason for this enhancement is the interaction between the exciton and high energy inter-band electron-hole transitions. This fact is validated by calculating the absorption spectra under the influence of an external electric field. The electron energy loss spectra is shown to change dramatically as a function of ${\bf q}$.

View original: http://arxiv.org/abs/1204.2724