for distribution - thanks

[CM ICTP - Trieste]

JOINT ICTP/SISSA STATISTICAL PHYSICS SEMINAR



Friday, 1 February    -    11:00 a.m.



Seminar Room - ICTP Main Building  (first floor)

	


M. MÜLLER ( Harvard University )



"Quantum electron glasses and electron assisted hopping"



Abstract

Insulators close to the metal insulator transition exhibit interesting 
collective electronic phenomena which are still rather poorly 
understood.   A prominent feature in such systems is the purely 
electronic nature of activated transport apparent in experiments, which 
is inconsistent with the theory of phonon-assisted hopping conduction 
and thus has remained an unexplained puzzle for decades.  The situation 
became even less clear when recently theories of many body localization 
predicted a metal insulator transition at finite temperature for 
interacting electrons that are decoupled from phonons.
In this talk I will address this problem for Anderson insulators with a 
single-particle localization length much larger than the mean distance 
between electrons.  Under these circumstances Coulomb interactions 
drive the electrons into a strongly correlated quantum glass phase with 
non-trivial collective behavior.  I will show that a typical metastable 
state exhibits a gapless spectrum of collective excitations which act 
as a bath with which individual electrons can exchange energy. In 2D 
systems,  this results in a hopping transport mechanism with a nearly 
universal pre-exponential factor of order e2/h.  This is in good 
agreement with many recent experiments.