Nonequilibrium Bethe-Salpeter equation for transient photoabsorption spectroscopy

E. Perfetto, D. Sangalli, A. Marini, and G. Stefanucci
Phys. Rev. B 92, 205304 – Published 12 November 2015

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.

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  • Received 3 July 2015
  • Revised 16 October 2015

DOI:https://doi.org/10.1103/PhysRevB.92.205304

©2015 American Physical Society

Authors & Affiliations

E. Perfetto1,2, D. Sangalli3, A. Marini3, and G. Stefanucci1,2

  • 1Dipartimento di Fisica, Università di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome, Italy and European Theoretical Spectroscopy Facility (ETSF)
  • 2INFN, Laboratori Nazionali di Frascati, Via E. Fermi 40, 00044 Frascati, Italy
  • 3Istituto di Struttura della Materia of the National Research Council, Via Salaria Km 29.3, I-00016 Montelibretti, Italy and European Theoretical Spectroscopy Facility (ETSF)

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Issue

Vol. 92, Iss. 20 — 15 November 2015

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