Universal out-of-equilibrium transport in Kondo-correlated quantum dots

TL;DR

This paper critically examines previous calculations of self energies and Green functions in non-equilibrium transport through quantum dots, revealing errors that compromise current conservation and the reliability of earlier results.

Contribution

It identifies and corrects inaccuracies in earlier theoretical work on non-equilibrium transport in Kondo-correlated quantum dots, emphasizing the importance of proper self energy calculations.

Findings

Previous self energy calculations were incorrect.

Corrected self energies restore current conservation.

Earlier results are unreliable due to these errors.

Abstract

It is shown that the lesser and greater self energies and Green functions calculated in a recent work on universal noequilibrium transport in interacting quantum dots [E. Mu\~noz, C. J. Bolech, and S. Kirchner, Phys. Rev. Lett. 110, 016601 (2013)] are incorrect. The authors start from renormalized second-order perturbation theory in the Coulomb repulsion in the particle-hole symmetric impurity Anderson model. The reported lesser self-energy is compared with the correct one, and with an analytic result valid for small frequency and applied voltage. As a consequence of the mistakes, the conservation of the current is not established and the results are unreliable.