Charge-relaxation and dwell time in the fluctuating admittance of a chaotic cavity

¹ Instituut-Lorentz, University of Leiden - P.O. Box 9506, 2300 RA Leiden, The Netherlands
² Département de Physique Théorique, Université de Genève - CH-1211 Genève 4, Switzerland

Received: 18 October 1996
Accepted: 28 January 1997

Abstract

We consider the admittance of a chaotic quantum dot, capacitively coupled to a gate and connected to two electron reservoirs by multichannel ballistic point contacts. For a dot in the regime of weak localization and universal conductance fluctuations, we calculate the average and variance of the admittance using random-matrix theory. We find that the admittance is governed by two time scales: the classical admittance depends on the RC time τ of the quantum dot, but the relevant time scale for the weak-localization correction and the admittance fluctuations is the dwell time. An extension of the circular ensemble is used for a statistical description of the energy dependence of the scattering matrix.