Seminars of the Department of Theoretical Physics

[liguori at ts.infn.it]

Wednesday 20 May 2009 - 15.00 hrs
Room 204 (ICTP - LB 2nd floor)

Gaetano SENATORE
(University of Trieste and CNR-INFM DEMOCRITOS)

MODELING THE TWO-DIMENSIONAL ELECTRON GAS IN SOLID STATE DEVICES

Abstract
Confining systems of many particles to move in reduced dimensions (2,1,0)
affects their properties in an important manner yielding peculiar
phenomena that continue to attract the attention of experimental,
theoretical and computational physicists alike.  Sticking to electron
systems in 2 dimensions (2D), one may mention the quantum Hall effect, 
electrons in graphene sheets (Dirac Fermions), the metal-insulator
transition. The simplest toy model to study many of these systems is the
so called electron gas, a collection of point charged Fermions moving in a
homogeneous neutralizing background.
After a very brief introduction, I shall discuss recent progress in the
modeling of 2D electron systems of exceedingly high mobility, as realized
in solid state devices such as quantum wells and FETs, concentrating on
the regime relevant to the observation of the metal-insulator transition.
These electrons are in fact quasi-2D (there is  a residual transverse
thickenss), suffer a weak scattering from various sources, and, depending
on the device, may possess an additional discrete (valley) degeneracy
and/or an in-plane anysotropic mass. I shall argue that the 2D electron
gas is perfectly capable of describing  experimental evidence available
for such systems, once the model is augmented with important device
details, a crucial one being disorder scattering. I shall also argue that
an extremely accurate treatment of the model is necessary and that in this
respect the only appropriate technique to date is provided by Quantum
Monte Carlo.