335 research outputs found
Interacting electrons in a two-dimensional disordered environment: Effect of a Zeeman magnetic field
The effect of a Zeeman magnetic field coupled to the spin of the electrons on
the conducting properties of the disordered Hubbard model is studied. Using the
Determinant Quantum Monte Carlo method, the temperature- and magnetic-field-
dependent conductivity is calculated,as well as the degree of spin
polarization. We find that the Zeeman magnetic field suppresses the metallic
behavior present for certain values of interaction- and disorder- strength, and
is able to induce a metal-insulator transition at a critical field strength. It
is argued that the qualitative features of magnetoconductance in this
microscopic model containing both repulsive interactions and disorder are in
agreement with experimental findings in two-dimensional electron- and
hole-gases in semiconductor structures.Comment: 4 pages, 4 figure
Solitons in Trapped Bose-Einstein condensates in one-dimensional optical lattices
We use Quantum Monte Carlo simulations to show the presence and study the
properties of solitons in the one dimensional soft-core bosonic Hubbard model
with near neighbor interaction in traps. We show that when the half-filled
Charge Density Wave (CDW) phase is doped, solitons are produced and quasi long
range order established. We discuss the implications of these results for the
presence and robustness of this solitonic phase in Bose-Einstein Condensates
(BEC) on one dimensional optical lattices in traps and study the associated
excitation spectrum. The density profile exhibits the coexistence of Mott
insulator, CDW, and superfluid regions.Comment: 5 pages, Latex with figure
Phase separation in the bosonic Hubbard model with ring exchange
We show that soft core bosons in two dimensions with a ring exchange term
exhibit a tendency for phase separation. This observation suggests that the
thermodynamic stability of normal bose liquid phases driven by ring exchange
should be carefully examined.Comment: 4 pages, 6 figure
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