In this work we put forward a first-principles approach and propose an accurate diagrammatic approximation to calculate the time-resolved (TR) and angle-resolved photoemission spectrum of systems with excitons. We also derive an alternative formula to the TR photocurrent which involves a single time-integral of the lesser Green's function. The diagrammatic approximation applies to the relaxed regime characterized by the presence of quasistationary excitons and vanishing polarization. The nonequilibrium self-energy diagrams are evaluated using excited Green's functions; since this is not standard, the analytic derivation is presented in detail. The final result is an expression for the lesser Green's function in terms of quantities that can all be calculated in a first-principles manner. The validity of the proposed theory is illustrated in a one-dimensional model system with a direct gap. We discuss possible scenarios and highlight some universal features of the exciton peaks. Our results indicate that the exciton dispersion can be observed in TR and angle-resolved photoemission.

Perfetto, E., Sangalli, D., Marini, A., Stefanucci, G. (2016). First-principles approach to excitons in time-resolved and angle-resolved photoemission spectra. PHYSICAL REVIEW. B, 94(24) [10.1103/PhysRevB.94.245303].

First-principles approach to excitons in time-resolved and angle-resolved photoemission spectra

Perfetto, E;STEFANUCCI, GIANLUCA
2016-01-01

Abstract

In this work we put forward a first-principles approach and propose an accurate diagrammatic approximation to calculate the time-resolved (TR) and angle-resolved photoemission spectrum of systems with excitons. We also derive an alternative formula to the TR photocurrent which involves a single time-integral of the lesser Green's function. The diagrammatic approximation applies to the relaxed regime characterized by the presence of quasistationary excitons and vanishing polarization. The nonequilibrium self-energy diagrams are evaluated using excited Green's functions; since this is not standard, the analytic derivation is presented in detail. The final result is an expression for the lesser Green's function in terms of quantities that can all be calculated in a first-principles manner. The validity of the proposed theory is illustrated in a one-dimensional model system with a direct gap. We discuss possible scenarios and highlight some universal features of the exciton peaks. Our results indicate that the exciton dispersion can be observed in TR and angle-resolved photoemission.
2016
Pubblicato
Rilevanza internazionale
Articolo
Sì, ma tipo non specificato
Settore FIS/03 - FISICA DELLA MATERIA
English
Electronic, Optical and Magnetic Materials; Condensed Matter Physics
http://harvest.aps.org/bagit/articles/10.1103/PhysRevB.94.245303/apsxml
Perfetto, E., Sangalli, D., Marini, A., Stefanucci, G. (2016). First-principles approach to excitons in time-resolved and angle-resolved photoemission spectra. PHYSICAL REVIEW. B, 94(24) [10.1103/PhysRevB.94.245303].
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/2108/174022
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