6533b828fe1ef96bd12883d2
RESEARCH PRODUCT
Diagrammatic Expansion for Positive Spectral Functions in the Steady-State Limit
Daniel KarlssonMarkku HyrkäsRobert Van Leeuwensubject
010302 applied physicsSteady state (electronics)Statistical Mechanics (cond-mat.stat-mech)non-equilibrium Green's functionsFOS: Physical sciences02 engineering and technologyPositive-definite matrix021001 nanoscience & nanotechnologyCondensed Matter Physics01 natural sciencesElectronic Optical and Magnetic MaterialsDiagrammatic reasoningspectral propertiesFrequency domainProduct (mathematics)0103 physical sciencesApplied mathematicsLimit (mathematics)Perturbation theory (quantum mechanics)0210 nano-technologyRepresentation (mathematics)kvanttifysiikkaCondensed Matter - Statistical MechanicsMathematicsperturbation theorydescription
Recently, a method was presented for constructing self-energies within many-body perturbation theory that are guaranteed to produce a positive spectral function for equilibrium systems, by representing the self-energy as a product of half-diagrams on the forward and backward branches of the Keldysh contour. We derive an alternative half-diagram representation that is based on products of retarded diagrams. Our approach extends the method to systems out of equilibrium. When a steady-state limit exists, we show that our approach yields a positive definite spectral function in the frequency domain.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2019-01-01 |