Superlattices and Microstructures 33 (2003) 181–192 www.elsevier.com/locate/jnlabr/yspmi Effect of an ac field on the conductance fluctuations for mescoscopic systems Godfrey Gumbs a,∗ , Jakob Rhyner b a Department of Physics and Astronomy, Hunter College of CUNY and the Graduate School, 695 Park Avenue, New York, NY 10021, USA b Asea Brown Boveri, Corporate Research, CH-5405, Baden-Dattwil, Switzerland Received 23 May 2003; received in revised form 23 May 2003; accepted 27 August 2003 Abstract With the use of perturbation theory to perform impurity averaging, the conductance fluctuations (CF) in mesoscopic systems are evaluated at finite frequency (ω) of the applied electric field. Calculations are carried out for frequencies much smaller than the inverse elastic mean free time, ω ≪ τ -1 el . It is shown that the CF decrease monotonically as ω increases. Also, the frequency scale over which this decrease occurs is given by τ -1 diff ≪ τ -1 el , where τ diff is the time for an electron to diffuse across the sample. This means that the universality of the CF at zero frequency is not preserved at finite frequency. These calculations are for a rectangular prism. Six leads covering the probe faces are attached to the cube. It is also shown that at finite frequency the sample-to-sample CF have the same size as the fluctuations of a given sample as a function of frequency. © 2003 Elsevier Ltd. All rights reserved. PACS: 73.23.-b 1. Introduction There has been a considerable amount of theoretical and experimental interest in the conductance fluctuations (CF) of mesoscopic metallic probes [1–11]. Under experimental conditions where the coherence of the electron wavefunction is either only weakly perturbed or remains the same throughout the entire sample, the transport characteristics do not only depend on average quantities such as the impurity concentration but also on specific details of the sample, such as the impurity configuration and the shape of the sample. Consequently, the conductance varies from sample to sample as a random, ∗ Corresponding author. Tel.: +1-212-6503935; fax: +1-212-772-5390. E-mail address: ggumbs@hunter.cuny.edu (G. Gumbs). 0749-6036/$ - see front matter © 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0749-6036(03)00080-6