New Study of Shot Noise Based on the Nonequilibrium Kubo Formula in Mesoscopic Systems: Application to the Kondo Effect in a Quantum Dot

Abstract

Recently, we have developed a theory of Keldysh formalism for mesoscopic systems. The resulting nonequilibrium Kubo formula for differential conductance makes it possible to propose a new formula of the shot noise S h , and thus to study shot noise in correlated systems at any temperature and any bias voltage. Employing this new approach, we analyze shot noise in the Kondo regime through a quantum dot in a symmetric case at zero temperature. Using the renormalized perturbation theory, we prove that, in the leading order of bias voltage, S h is equal to the noise power at zero temperature conventionally used as shot noise. With S h , we calculate the Fano factor for the backscattering current I b : F b = S h /2 e I b . It is shown that the Fano factor takes the universal form of F b =1+4( R -1) 2 /[1+5( R -1) 2 ] determined by the Wilson ratio R for an arbitrary strength of the Coulomb interaction. Using the Wilson ratio R =2, our result coincides with the fractional value of F b =5/3 derived in the Kondo ...