6 research outputs found
Critical Quantum Chaos in 2D Disordered Systems with Spin-Orbit Coupling
We examine the validity of the recently proposed semi-Poisson level spacing
distribution function P(S), which characterizes `critical quantum chaos', in 2D
disordered systems with spin-orbit coupling. At the Anderson transition we show
that the semi-Poisson P(S) can describe closely the critical distribution
obtained with averaged boundary conditions, over Dirichlet in one direction
with periodic in the other and Dirichlet in both directions. We also obtain a
sub-Poisson linear number variance ,
with asymptotic value . The obtained critical statistics,
intermediate between Wigner and Poisson, is relevant for disordered systems and
chaotic models.Comment: 4 pages with 5 figure
Ground state of a partially melted Wigner molecule
We consider three spinless fermions free to move on 2d square lattice with
periodic boundary conditions and interacting via a U/r Coulomb repulsion. When
the Coulomb energy to kinetic energy ratio r_s is large, a rigid Wigner
molecule is formed. As r_s decreases, we show that melting proceeds via an
intermediate regime where a floppy two particle molecule coexists with a
partially delocalized particle. A simple ansatz is given to describe the ground
state of this mesoscopic solid-liquid regime.Comment: to appear in Europhysics Letter
Role of a parallel magnetic field in two dimensional disordered clusters containing a few correlated electrons
An ensemble of 2d disordered clusters with a few electrons is studied as a
function of the Coulomb energy to kinetic energy ratio r_s. Between the Fermi
system (small r_s) and the Wigner molecule (large r_s), an interaction induced
delocalization of the ground state takes place which is suppressed when the
spins are aligned by a parallel magnetic field. Our results confirm the
existence of an intermediate regime where the Wigner antiferromagnetism
defavors the Stoner ferromagnetism and where the enhancement of the Lande g
factor observed in dilute electron systems is reproduced.Comment: 4 pages, 3 figure