Conductance Fluctuations in a Disordered Double-Barrier Junction

Abstract

We consider the effect of disorder on coherent tunneling through two barriers in series, in the regime of overlapping transmission resonances. We present analytical calculations (using random-matrix theory) and numerical simulations (on a lattice) to show that strong mode-mixing in the inter-barrier region induces mesoscopic fluctuations in the conductance $G$ of universal magnitude $e^2/h$ for a symmetric junction. For an asymmetric junction, the root-mean-square fluctuations depend on the ratio $\nu$ of the two tunnel resistances according to $rmsG=(4e^2/h){\beta }^{-1/2}\nu (1+\nu {)}^{-2}$, where $\beta =1(2)$ in the presence (absence) of time-reversal symmetry.

12 pages, REVTeX-3.0, 2 figures, submitted to Physical Review B