Weak Charge Quantization as an Instanton of the InteractingσModel

Abstract

Coulomb blockade in a quantum dot attached to a diffusive conductor is considered in the framework of the nonlinear $\sigma$ model. It is shown that the weak charge quantization on the dot is associated with instanton configurations of the $Q$ field in the conductor. The instantons have a finite action and are replica nonsymmetric. It is argued that such instantons may play a role in the transition regime to the interacting insulator.