Analytical continuation of matrix-valued functions: Carathéodory formalism
Journal Article
·
· Physical Review. B
- Univ. of Michigan, Ann Arbor, MI (United States); OSTI
- Univ. of Michigan, Ann Arbor, MI (United States)
Finite-temperature quantum field theories are formulated in terms of Green's functions and self-energies on the Matsubara axis. In multiorbital systems, these quantities are related to positive semidefinite matrix-valued functions of the Carathéodory and Schur class. Analysis, interpretation, and evaluation of derived quantities such as real-frequency response functions requires analytic continuation of the off-diagonal elements to the real axis. Here we derive the criteria under which such functions exist for given Matsubara data and present an interpolation algorithm that intrinsically respects their mathematical properties. For small systems with precise Matsubara data, we find that the continuation exactly recovers all off-diagonal and diagonal elements. In real-materials systems, we show that the precision of the continuation is sufficient for the analytic continuation to commute with the Dyson equation, and we show that the truncation of the off-diagonal self-energy elements leads to considerable approximation artifacts.
- Research Organization:
- Emory Univ., Atlanta, GA (United States)
- Sponsoring Organization:
- USDOE; USDOE Office of Science (SC)
- Grant/Contract Number:
- SC0019374
- OSTI ID:
- 1979671
- Alternate ID(s):
- OSTI ID: 1824703
- Journal Information:
- Physical Review. B, Journal Name: Physical Review. B Journal Issue: 16 Vol. 104; ISSN 2469-9950
- Publisher:
- American Physical Society (APS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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