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Extended Coupled Ladder Approximation for Keldysh FRG

Lukas Weidinger

23.02.2017 at 12:15 

In a recent work [1], we introduced in the framework of Matsubra fRG the extended Coupled Ladder Approximation (eCLA) for the treatment of quantum point contacts (QPCs). Like in other Coupled Ladder Approximations schemes, the two-particle vertex is split in three frequency channels, which interact only via static feedback.
In previous works on QPCs with short ranged interactions, this feedback was taken local in position space. For the treatment of longer ranged interactions it is, however, necessary to allow for a extended range of this feedback, leading naturally to the eCLA.
In [1] only a static version of the eCLA was implemented, showing the principal feasability of the concept and giving a first impression of its value in applications on QPCs and quantum dots.
Our current work is concerned with the development of a eCLA scheme in the framework of the more general Keldysh fRG. This will allow us to explore dynamic observables on the real frequency axis, and makes - at least in principle - also non-equilibrium quantities accessible.

[1] L. Weidinger, F. Bauer, J. von Delft, Phys. Rev. B 95, 035122

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