Fermi liquid theory for the nonequilibrium Kondo effect at low bias voltages

Akira Oguri

doi:10.1143/JPSJ.74.110

paper

Fermi liquid theory for the nonequilibrium Kondo effect at low bias voltages

arXiv:cond-mat/0412220 · doi:10.1143/JPSJ.74.110

Abstract

In this report, we describe a recent development in a Fermi liquid theory for the Kondo effect in quantum dots under a finite bias voltage $V$ . Applying the microscopic theory of Yamada and Yosida to a nonequilibrium steady state, we derive the Ward identities for the Keldysh Green's function, and determine the low-energy behavior of the differential conductance $d I / d V$ exactly up to terms of order $(e V)^{2}$ for the symmetric Anderson model. These results are deduced from the fact that the Green's function at the impurity site is a functional of a nonequilibrium distribution $f_{eff} (ω)$ , which at $e V = 0$ coincides with the Fermi function. Furthermore, we provide an alternative description of the low-energy properties using a renormalized perturbation theory (RPT). In the nonequilibrium state the unperturbed part of the RPT is determined by the renormalized free quasiparticles, the distribution function of which is given by $f_{eff} (ω)$ . The residual interaction between the quasiparticles $U$ , which is defined by the full vertex part at zero frequencies, is taken into account by an expansion in the power series of $U$ . We also discuss the application of the RPT to a high-bias region beyond the Fermi-liquid regime.

8 pages, to appear in a special edition of JPSJ "Kondo Effect -- 40 Years after the Discovery", typos are corrected

Fermi liquid theory for the nonequilibrium Kondo effect at low bias voltages

Abstract

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