TY - JOUR
T1 - Improved Dielectric Response of Solids
T2 - Combining the Bethe-Salpeter Equation with the Random Phase Approximation
AU - Søndersted, Amalie H.
AU - Kuisma, Mikael
AU - Svaneborg, Jakob K.
AU - Svendsen, Mark Kamper
AU - Thygesen, Kristian S.
N1 - Publisher Copyright:
© 2024 American Physical Society.
PY - 2024
Y1 - 2024
N2 - The Bethe-Salpeter equation (BSE) can provide an accurate description of low-energy optical spectra of insulating crystals - even when excitonic effects are important. However, due to high computational costs it is only possible to include a few bands in the BSE Hamiltonian. As a consequence, the dielectric screening given by the real part of the dielectric function can be significantly underestimated by the BSE. Here, we show that universally accurate optical response functions can be obtained by combining a four-point BSE-like equation for the irreducible polarizability with a two-point Dyson equation that includes the higher-lying transitions within the random phase approximation. The new method is referred to as BSE+. It has a computational cost comparable to the BSE but a much faster convergence with respect to the size of the electron-hole basis. We use the method to calculate refractive indices and electron energy loss spectra for a test set of semiconductors and insulators. In all cases the BSE+ yields excellent agreement with experimental data across a wide frequency range and outperforms both the BSE and the random phase approximation.
AB - The Bethe-Salpeter equation (BSE) can provide an accurate description of low-energy optical spectra of insulating crystals - even when excitonic effects are important. However, due to high computational costs it is only possible to include a few bands in the BSE Hamiltonian. As a consequence, the dielectric screening given by the real part of the dielectric function can be significantly underestimated by the BSE. Here, we show that universally accurate optical response functions can be obtained by combining a four-point BSE-like equation for the irreducible polarizability with a two-point Dyson equation that includes the higher-lying transitions within the random phase approximation. The new method is referred to as BSE+. It has a computational cost comparable to the BSE but a much faster convergence with respect to the size of the electron-hole basis. We use the method to calculate refractive indices and electron energy loss spectra for a test set of semiconductors and insulators. In all cases the BSE+ yields excellent agreement with experimental data across a wide frequency range and outperforms both the BSE and the random phase approximation.
U2 - 10.1103/PhysRevLett.133.026403
DO - 10.1103/PhysRevLett.133.026403
M3 - Journal article
C2 - 39073962
AN - SCOPUS:85198567725
SN - 0031-9007
VL - 133
JO - Physical Review Letters
JF - Physical Review Letters
IS - 2
M1 - 026403
ER -