Current Noise in Non-Chiral Luttinger Liquids: Appearance of Fractional Charge

Abstract

The current noise of a voltage‐biased interacting quantum wire connected to leads is computed in presence of an impurity in the wire. We find that in the weak backscattering limit the Fano factor characterizing the ratio between noise and backscattered current crucially depends on the noise frequency ω relative to the ballistic frequency vF/gL, where vF is the Fermi velocity, g the electron interaction strength, and L the length of the wire. In contrast to chiral Luttinger liquids, the noise is not only due to the Poissonian backscattering of fractionally charged quasiparticles at the impurity, but also to Andreev‐type reflections at the contacts. The frequency dependence of the noise needs to be analyzed to extract the fractional charge e* = eg of the bulk excitations.