Workshop book - Physikzentrum der RWTH Aachen - RWTH Aachen ...

Posters Monday February 4
Poster 14:
Fermionic superoperators in application to non-linear transport: real-time
renormalization group, time-evolution and exact relations for Anderson
quantum dots.
Roman Saptsov
We introduced a new formalism of fermionic superoperators in Liouville-
Fock space to enable a real-time renormalization group analysis of the nonequilibrium
Anderson model in the stationary state. The RT-RG equations
were solved numerically including both 1- and 2- loop orders in the limit of
zero temperature and non-linear transport voltages where most standard theoretical
methods break down. We predict non-perturbative tunneling effects
in the transport stability diagram which can be measured experimentally.
Moreover, we found the exact functional form of the renormalized spectra of
the dot at any loop order. In the strong-interacting limit the method breaks
down as expected only at very small voltages on the order of the Kondo
temperature, which we illustrate by comparison with the Friedel sum rule.
For the time dependent non-interacting case with help of fermionic superoperators
we show that the perturbation expansion in tunnel coupling automatically
truncates at the second loop and discuss solutions in the Wide Band
Limit and beyond of it. We also discuss extension of our time-dependent
results to the weakly interacting case.
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