5,904 research outputs found
Broken-Symmetry States of Dirac Fermions in Graphene with A Partially Filled High Landau Level
We report on numerical study of the Dirac fermions in partially filled N=3
Landau level (LL) in graphene. At half-filling, the equal-time density-density
correlation function displays sharp peaks at nonzero wavevectors . Finite-size scaling shows that the peak value grows with electron
number and diverges in the thermodynamic limit, which suggests an instability
toward a charge density wave. A symmetry broken stripe phase is formed at large
system size limit, which is robust against purturbation from disorder
scattering. Such a quantum phase is experimentally observable through transport
measurements. Associated with the special wavefunctions of the Dirac LL, both
stripe and bubble phases become possible candidates for the ground state of the
Dirac fermions in graphene with lower filling factors in the N=3 LL.Comment: Contains are slightly changed. Journal reference and DOI are adde
Particle-Hole Symmetry Breaking and the 5/2 Fractional Quantum Hall Effect
We report on the study of the fractional quantum Hall effect at the filling
factor 5/2 using exact diagonalization method with torus geometry. The
particle-hole symmetry breaking effect is considered using an additional
three-body interaction. Both Pfaffian and anti-Pfaffian states can be the
ground state depending on the sign of the three-body interaction. The results
of the low-energy spectrum, the wave function overlap, and the particle-hole
parity evolution, have shown the clear evidence of a direct sharp transition
(possibly first-order) from the Pfaffian to the anti-Pfaffian state at the
Coulomb point. A quantum phase diagram is established, where one finds further
transitions from the Pfaffian or anti-Pfaffian state to the nearby compressible
phases induced by a change of the pseudopotential.Comment: 4 pages, 4 figure
Search for the signal of monotop production at the early LHC
We investigate the potential of the early LHC to discover the signal of
monotops, which can be decay products of some resonances in models such as
R-parity violating SUSY or SU(5), etc. We show how to constrain the parameter
space of the models by the present data of boson hadronic decay branching
ratio, mixing and dijet productions at the LHC. Then, we study
the various cuts imposed on the events, reconstructed from the hadronic final
states, to suppress backgrounds and increase the significance in detail. And we
find that in the hadronic mode the information from the missing transverse
energy and reconstructed resonance mass distributions can be used to specify
the masses of the resonance and the missing particle. Finally, we study the
sensitivities to the parameters at the LHC with =7 TeV and an
integrated luminosity of in detail. Our results show that the
early LHC may detect this signal at 5 level for some regions of the
parameter space allowed by the current data.Comment: 25 pages, 18 figures, 3 tables, version published in Phys.Rev.
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