In this work, we propose an accurate first-principles approach to calculate the transient photoabsorption spectrum measured in pump-and-probe experiments. We formulate a condition of adiabaticity and thoroughly analyze the simplifications brought about by the fulfillment of this condition in the nonequilibrium Green's function (NEGF) framework. Starting from the Kadanoff-Baym equations, we derive a nonequilibrium Bethe-Salpeter equation (BSE) for the response function that can be implemented in most of the already existing ab initio codes. In addition, the adiabatic approximation is benchmarked against full NEGF simulations in simple model Hamiltonians, even under extreme, nonadiabatic conditions in which it is expected to fail. We find that the nonequilibrium BSE is very robust and captures important spectral features in a wide range of experimental configurations.

Perfetto, E., Sangalli, D., Marini, A., Stefanucci, G. (2015). Nonequilibrium Bethe-Salpeter equation for transient photoabsorption spectroscopy. PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS, 92(20) [10.1103/PhysRevB.92.205304].

Nonequilibrium Bethe-Salpeter equation for transient photoabsorption spectroscopy

Perfetto, E;STEFANUCCI, GIANLUCA
2015-01-01

Abstract

In this work, we propose an accurate first-principles approach to calculate the transient photoabsorption spectrum measured in pump-and-probe experiments. We formulate a condition of adiabaticity and thoroughly analyze the simplifications brought about by the fulfillment of this condition in the nonequilibrium Green's function (NEGF) framework. Starting from the Kadanoff-Baym equations, we derive a nonequilibrium Bethe-Salpeter equation (BSE) for the response function that can be implemented in most of the already existing ab initio codes. In addition, the adiabatic approximation is benchmarked against full NEGF simulations in simple model Hamiltonians, even under extreme, nonadiabatic conditions in which it is expected to fail. We find that the nonequilibrium BSE is very robust and captures important spectral features in a wide range of experimental configurations.
2015
Pubblicato
Rilevanza internazionale
Articolo
Sì, ma tipo non specificato
Settore FIS/03 - FISICA DELLA MATERIA
English
Electronic, Optical and Magnetic Materials; Condensed Matter Physics
Perfetto, E., Sangalli, D., Marini, A., Stefanucci, G. (2015). Nonequilibrium Bethe-Salpeter equation for transient photoabsorption spectroscopy. PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS, 92(20) [10.1103/PhysRevB.92.205304].
Perfetto, E; Sangalli, D; Marini, A; Stefanucci, G
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2108/173986
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