title: Full counting statistics for orbital-degenerate impurity Anderson model with Hund's rule exchange coupling.
abstract: We study nonequilibrium current fluctuations through a quantum dot, which includes a ferromagnetic Hund's rule coupling J, in the low-energy Fermi liquid regime using the renormalized perturbation theory. The resulting cumulant for the current distribution in the particle-hole symmetric case shows that spin-triplet and spin-singlet pairs of quasiparticles are formed in the current due to the Hund's rule coupling, and these pairs enhance the current fluctuations. In the fully screened higher-spin Kondo limit, the Fano factor takes a value F(b)=(9M+6)/(5M+4) determined by the orbital degeneracy M. We also investigate the crossover between the small and large J limits in the two-orbital case M=2, using the numerical renormalization group approach.
authors.affiliation: Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo, Japan.
authors.forename: Rui
authors.initials: R
authors.lastname: Sakano
authors.forename: Yunori
authors.initials: Y
authors.lastname: Nishikawa
authors.forename: Akira
authors.initials: A
authors.lastname: Oguri
authors.forename: Alex C
authors.initials: AC
authors.lastname: Hewson
authors.forename: Seigo
authors.initials: S
authors.lastname: Tarucha