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Published on: August 19, 2021
Extracting spectral properties from Keldysh Green functions.
Andreas Dirks1, Martin Eckstein, Thomas Pruschke
1Department of Physics, University of Göttingen, D-37077 Göttingen, Germany.
Summary
Extending imaginary-time simulations to a finite Schwinger-Keldysh contour improves spectral property calculations for quantum systems. Combining real-time and imaginary-time data enhances resolution across different energy scales.
Area of Science:
- Quantum many-body physics
- Computational physics
- Statistical mechanics
Background:
- Calculating spectral properties of interacting quantum systems is numerically challenging.
- Standard methods often struggle with ill-posed problems in thermal equilibrium.
Purpose of the Study:
- To improve the numerical calculation of spectral properties for interacting quantum systems.
- To investigate extending imaginary-time simulations using a finite Schwinger-Keldysh contour.
Main Methods:
- Extended imaginary-time simulation to a finite Schwinger-Keldysh contour.
- Applied the maximum entropy approach for analytic continuation.
- Tested on spectral properties of interacting quantum systems in thermal equilibrium.
Main Results:
- Including real-time data enhances high-energy structure resolution.
- Imaginary-time data are crucial for accurately capturing low-frequency features like quasiparticle peaks.
- The extended method shows promise for nonequilibrium applications, like calculating time-dependent spectral functions.
Conclusions:
- The finite Schwinger-Keldysh contour extension aids in numerically ill-posed spectral property calculations.
- A hybrid approach using both real- and imaginary-time data offers improved accuracy.
- This method provides a viable alternative to direct Fourier transformation and Padé approximants for time-dependent spectral functions.
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