75 research outputs found
Incompressible Even Denominator Fractional Quantum Hall States in the Zeroth Landau Level of Monolayer Graphene
Incompressible even denominator fractional quantum Hall states at fillings
and have been recently observed
in monolayer graphene. We use a Chern-Simons description of multi-component
fractional quantum Hall states in graphene to investigate the properties of
these states and suggest variational wavefunctions that may describe them. We
find that the experimentally observed even denominator fractions and standard
odd fractions (such as , etc.) can be accommodated within the
same flux attachment scheme and argue that they may arise from sublattice or
chiral symmetry breaking orders (such as charge-density-wave and
antiferromagnetism) of composite Dirac fermions, a phenomenon unifying integer
and fractional quantum Hall physics for relativistic fermions. We also discuss
possible experimental probes that can narrow down the candidate broken symmetry
phases for the fractional quantum Hall states in the zeroth Landau level of
monolayer graphene.Comment: 5 page
Contour-time approach to the Bose-Hubbard model in the strong coupling regime: Studying two-point spatio-temporal correlations at the Hartree-Fock-Bogoliubov level
We develop a formalism that allows the study of correlations in space and
time in both the superfluid and Mott insulating phases of the Bose-Hubbard
Model. Specifically, we obtain a two particle irreducible effective action
within the contour-time formalism that allows for both equilibrium and out of
equilibrium phenomena. We derive equations of motion for both the superfluid
order parameter and two-point correlation functions. To assess the accuracy of
this formalism, we study the equilibrium solution of the equations of motion
and compare our results to existing strong coupling methods as well as exact
methods where possible. We discuss applications of this formalism to out of
equilibrium situations.Comment: 41 pages, 7 figures. arXiv admin note: substantial text overlap with
arXiv:1606.0411
Asymmetric spatial structure of zero modes for birefringent Dirac fermions
We study the zero energy modes that arise in an unusual vortex configuration
involving both the kinetic energy and an appropriate mass term in a model which
exhibits birefringent Dirac fermions as its low energy excitations. We find the
surprising feature that the ratio of the length scales associated with states
centered on vortex and anti-vortex topological defects can be arbitrarily
varied but that fractionalization of quantum numbers such as charge is
unaffected. We discuss this situation from a symmetry point of view and present
numerical results for a specific lattice model realization of this scenario.Comment: 7 pages, 6 figure
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