For distribution

[CM ICTP - Trieste]

SEMINAR on  Disorder and strong electron correlations




Tuesday, 13 March   -    1:30 p.m.



Lecture Room 204,  Main Bldg.- second floor




P.W. BROUWER  ( Ludwig-Maximilians Universität, München and
  Cornell University, Ithaca )


"The classical limit of quantum transport"

Abstract

The interference of multiply scattered quantum mechanical matter waves 
causes small but noticeable corrections to the conductance of a metal 
at low temperatures.  Historically, one separates the interference 
correction to the electrical conductance into `weak localization', a 
small negative correction to the conductance averaged over an ensemble 
of conductors with different impurity configurations, and the 
'conductance fluctuations', the sample-to-sample fluctuations measured 
with respect to the ensemble average.  What is the fate of quantum 
interference corrections in the limit that the wavelength of the 
electrons becomes small in comparison to all other relevant length 
scales?  This limit is a 'classical limit' similar to the transition 
from wave optics to ray optics that occurs when the typical size of 
optical elements becomes much larger than the wavelength of light.  
I'll show that, whereas the interference correction to the 
ensemble-averaged conductance (weak localization) disappears in this 
classical limit, the quantum interference contribution to the 
sample-specific conductance fluctuations remains surprisingly 
unaffected.