313 research outputs found
Domain walls in gapped graphene
The electronic properties of a particular class of domain walls in gapped
graphene are investigated. We show that they can support mid-gap states which
are localized in the vicinity of the domain wall and propagate along its
length. With a finite density of domain walls, these states can alter the
electronic properties of gapped graphene significantly. If the mid-gap band is
partially filled,the domain wall can behave like a one-dimensional metal
embedded in a semi-conductor, and could potentially be used as a single-channel
quantum wire.Comment: 4 pgs. revte
Spin Versus Charge Density Wave Order in Graphene-like Systems
A variational technique is used to study sublattice symmetry breaking by
strong on-site and nearest neighbor interactions in graphene. When interactions
are strong enough to break sublattice symmetry, and with relative strengths
characteristic of graphene, a charge density wave Mott insulator is favored
over the spin density wave condensates. In the spin density wave condensate we
find that introduction of a staggered on-site energy (quasiparticle mass) leads
to a splitting of the fermi velocities and mass gaps of the quasiparticle spin
states.Comment: 5 pages, 4 figures; some comments adde
A Holographic Quantum Hall Ferromagnet
A detailed numerical study of a recent proposal for exotic states of the
D3-probe D5 brane system with charge density and an external magnetic field is
presented. The state has a large number of coincident D5 branes blowing up to a
D7 brane in the presence of the worldvolume electric and magnetic fields which
are necessary to construct the holographic state. Numerical solutions have
shown that these states can compete with the the previously known chiral
symmetry breaking and maximally symmetric phases of the D3-D5 system. Moreover,
at integer filling fractions, they are incompressible with integer quantized
Hall conductivities. In the dual superconformal defect field theory, these
solutions correspond to states which break the chiral and global flavor
symmetries spontaneously. The region of the temperature-density plane where the
D7 brane has lower energy than the other known D5 brane solutions is
identified. A hypothesis for the structure of states with filling fraction and
Hall conductivity greater than one is made and tested by numerical computation.
A parallel with the quantum Hall ferromagnetism or magnetic catalysis
phenomenon which is observed in graphene is drawn. As well as demonstrating
that the phenomenon can exist in a strongly coupled system, this work makes a
number of predictions of symmetry breaking patterns and phase transitions for
such systems.Comment: 38 pages, 7 figures, references adde
Correlators of the Kazakov-Migdal Model
We derive loop equations for the one-link correlators of gauge and scalar
fields in the Kazakov-Migdal model. These equations determine the solution of
the model in the large N limit and are similar to analogous equations for the
Hermitean two-matrix model. We give an explicit solution of the equations for
the case of a Gaussian, quadratic potential. We also show how similar
calculations in a non-Gaussian case reduce to purely algebraic equations.Comment: 14 pages, ITEP-YM-3-9
Topology and Duality in Abelian Lattice Theories
We show how to obtain the dual of any lattice model with inhomogeneous local
interactions based on an arbitrary Abelian group in any dimension and on
lattices with arbitrary topology. It is shown that in general the dual theory
contains disorder loops on the generators of the cohomology group of a
particular dimension. An explicit construction for altering the statistical sum
to obtain a self-dual theory, when these obstructions exist, is also given. We
discuss some applications of these results, particularly the existence of
non-trivial self-dual 2-dimensional Z_N theories on the torus. In addition we
explicitly construct the n-point functions of plaquette variables for the U(1)
gauge theory on the 2-dimensional g-tori.Comment: 11 pages, LateX, 1 epsf figure; minor typos corrected and references
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