Positivity of the Spectral Densities of Retarded Floquet Green Functions

Periodically driven nonequilibrium many-body systems are interesting because they have quasi-energy spectra, which can be tailored by controlling the external driving fields. We derive the general spectral representation of retarded Green functions in the Floquet regime, thereby generalizing the wel...

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Veröffentlicht in:Physical review letters 2019-04, Vol.122 (13), p.130604-130604, Article 130604
Hauptverfasser: Uhrig, Götz S, Kalthoff, Mona H, Freericks, James K
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Sprache:eng
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Zusammenfassung:Periodically driven nonequilibrium many-body systems are interesting because they have quasi-energy spectra, which can be tailored by controlling the external driving fields. We derive the general spectral representation of retarded Green functions in the Floquet regime, thereby generalizing the well-known Lehmann representation from equilibrium many-body physics. The derived spectral Floquet representation allows us to prove the non-negativity of spectral densities and to determine exact spectral sum rules, which can be employed to benchmark the accuracy of approximations to the exact Floquet many-body Green functions.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.122.130604