11,406 research outputs found
Hamiltonian Formulation of Quantum Hall Skyrmions with Hopf Term
We study the nonrelativistic nonlinear sigma model with Hopf term in this
paper. This is an important issue beacuse of its relation to the currently
interesting studies in skyrmions in quantum Hall systems. We perform the
Hamiltonian analysis of this system in variables. When the coefficient
of the Hopf term becomes zero we get the Landau-Lifshitz description of the
ferromagnets. The addition of Hopf term dramatically alters the Hamiltonian
analysis. The spin algebra is modified giving a new structure and
interpretation to the system. We point out momentum and angular momentum
generators and new features they bring in to the system.Comment: 16pages, Latex file, typos correcte
model with Hopf interaction: the quantum theory
The model with Hopf interaction is quantised following the
Batalin-Tyutin (BT) prescription. In this scheme, extra BT fields are
introduced which allow for the existence of only commuting first-class
constraints. Explicit expression for the quantum correction to the expectation
value of the energy density and angular momentum in the physical sector of this
model is derived. The result shows, in the particular operator ordering that we
have chosen to work with, that the quantum effect has a divergent contribution
of in the energy expectation value. But, interestingly
the Hopf term, though topological in nature, can have a finite contribution to energy density in the homotopically nontrivial
topological sector. The angular momentum operator, however, is found to have no
quantum correction, indicating the absence of any fractional spin even at this
quantum level. Finally, the extended Lagrangian incorporating the BT auxiliary
fields is computed in the conventional framework of BRST formalism exploiting
Faddeev-Popov technique of path integral method.Comment: LaTeX, 28 pages, no figures, typos corrected, journal ref. give
Why Do Granular Materials Stiffen with Shear Rate? : Test of Novel Stress-Based Statistics
Peer reviewedPublisher PD
Determinant Quantum Monte Carlo Study of the Screening of the One Body Potential near a Metal-Insulator Transition
In this paper we present a determinant quantum monte carlo study of the two
dimensional Hubbard model with random site disorder. We show that, as in the
case of bond disorder, the system undergoes a transition from an Anderson
insulating phase to a metallic phase as the onsite repulsion U is increased
beyond a critical value U_c. However, there appears to be no sharp signal of
this metal-insulator transition in the screened site energies. We observe that,
while the system remains metallic for interaction values upto twice U_c, the
conductivity is maximal in the metallic phase just beyond U_c, and decreases
for larger correlation.Comment: 6 pages, 10 eps figures, Revtex
Spin Polarizations at and about the Lowest Filled Landau Level
The spin polarization versus temperature at or near a fully filled lowest
Landau level is explored for finite-size systems in a periodic rectangular
geometry. Our results at which also include the finite-thickness
correction are in good agreement with the experimental results. We also find
that the interacting electron system results are in complete agreement with the
results of the sigma model, i.e., skyrmions on a torus have a topological
charge of and the Q=1 solution is like a single spin-flip excitation.
Our results therefore provide direct evidence for the skyrmionic nature of the
excitations at this filling factor.Comment: 4 pages, REVTEX, and 4 .ps files, To be published in Europhysics
Letter
A Fermi Fluid Description of the Half-Filled Landau Level
We present a many-body approach to calculate the ground state properties of a
system of electrons in a half-filled Landau level. Our starting point is a
simplified version of the recently proposed trial wave function where one
includes the antisymmetrization operator to the bosonic Laughlin state. Using
the classical plasma analogy, we calculate the pair-correlation function, the
static structure function and the ground state energy in the thermodynamic
limit. These results are in good agreement with the expected behavior at
.Comment: 4 pages, REVTEX, and 4 .ps file
Dynamical Correlations in a Half-Filled Landau Level
We formulate a self-consistent field theory for the Chern-Simons fermions to
study the dynamical response function of the quantum Hall system at .
Our scheme includes the effect of correlations beyond the random-phase
approximation (RPA) employed to this date for this system. The resulting
zero-frequency density response function vanishes as the square of the wave
vector in the long-wavelength limit. The longitudinal conductivity calculated
in this scheme shows linear dependence on the wave vector, like the
experimentals results and the RPA, but the absolute values are higher than the
experimental results.Comment: 4 pages, revtex, 3 figures included. Corrected typo
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