434 research outputs found
Second Virial Coefficient for Noncommutative Space
The second virial coefficient for non-interacting particles
moving in a two-dimensional noncommutative space and in the presence of a
uniform magnetic field is presented. The noncommutativity parameter
\te can be chosen such that the can be interpreted as the
second virial coefficient for anyons of statistics \al in the presence of
and living on the commuting plane. In particular in the high
temperature limit \be\lga 0, we establish a relation between the parameter
\te and the statistics \al. Moreover, can also be
interpreted in terms of composite fermions.Comment: 11 pages, misprints corrected and references adde
Feynman path-integral approach to the QED3 theory of the pseudogap
In this work the connection between vortex condensation in a d-wave
superconductor and the QED gauge theory of the pseudogap is elucidated. The
approach taken circumvents the use of the standard Franz-Tesanovic gauge
transformation, borrowing ideas from the path-integral analysis of the
Aharonov-Bohm problem. An essential feature of this approach is that
gauge-transformations which are prohibited on a particular multiply-connected
manifold (e.g. a superconductor with vortices) can be successfully performed on
the universal covering space associated with that manifold.Comment: 15 pages, 1 Figure. Int. J. Mod. Phys. B 17, 4509 (2003). Minor
changes from previous versio
Antiferromagnetism and phase separation in the t-J model at low doping: a variational study
Using Gutzwiller-projected wave functions, I estimate the ground-state energy
of the t-J model for several variational states relevant for high-temperature
cuprate superconductors. The results indicate antiferromagnetism and phase
separation at low doping both in the superconducting state and in the
staggered-flux normal state proposed for the vortex cores. While phase
separation in the underdoped superconducting state may be relevant for the
stripe formation mechanism, the results for the normal state suggest that
similar charge inhomogeneities may also appear in vortex cores up to relatively
high doping values.Comment: 4 pages, 3 figures, reference adde
Non-local order in gapless systems: Entanglement Spectrum in Spin Chains
We show that the entanglement spectrum can be used to define non-local order
in gapless spin systems. We find a gap that fully separates a series of
generic, high `entanglement energy' levels, from a flat band of levels with
specific multiplicities that uniquely define the ground-state, and remains
finite in the thermodynamic limit. We pick the appropriate set of quantum
numbers, and then partition the system in this space. This partition
corresponds to a very non-local real-space cut. Despite the fact that the
Laughlin state is bulk gapped while the antiferromagnetic spin chain state is
bulk gapless, we show that the S=1/2 Heisenberg antiferromagnet in one
dimension has an entanglement spectrum almost identical to that of the Laughlin
Fractional Quantum Hall state in two dimensions, revealing the similar field
theory of their low-energy edge and bulk excitations respectively.Comment: 4.5 pages, 3 figures; submitted to PRL on 10/08/09; revised version
plus supplementary materia
Critical Exponents in a Quantum Phase Transition of an Anisotropic 2D Antiferromagnet
I use the two-step density-matrix renormalization group method to extract the
critical exponents and in the transition from a N\'eel
phase to a magnetically disordered phase with a spin gap. I find
that the exponent computed from the magnetic side of the transition is
consistent with that of the classical Heisenberg model, but not the exponent
computed from the disordered side. I also show the contrast between
integer and half-integer spin cases.Comment: 4 pages, 2 figure
Free Relativistic Anyons with Canonical Spin Algebra
We discuss a relativistic free particle with fractional spin in 2+1
dimensions, where the dual spin components satisfy the canonical angular
momentum algebra . It is shown that it is a general consequence of these
features that the Poincar\`e invariance is broken down to the Lorentz one, so
indicating that it is not possible to keep simultaneously the free nature of
the anyon and the translational invariance.Comment: Complete version with reference
New Fermionic Description of Quantum S = 1/2 Antiferromargnet
A novel approach to S =1/2 antiferromagnets with strong fluctuations based on
the representation of spin-1/2 operators as bylinear forms of real (Majorana)
fermions is suggested. This representation has the advantage of being
irreducible without any constraints on the fermionic Hilbert space. This
property allows to derive an effective Hamiltonian for low-lying excitations in
the spin liquid state. It is proven that these excitations are S = 1 real
fermions.Comment: 4 page
Comment on "Statistical Mechanics of Non-Abelian Chern-Simons Particles"
The second virial coefficient for non-Abelian Chern-Simons particles is
recalculated. It is shown that the result is periodic in the flux parameter
just as in the Abelian theory.Comment: 3 pages, latex fil
Scenario for Fractional Quantum Hall Effect in Bulk Isotropic Materials
We investigate the possibility of a strongly correlated Fractional Quantum
Hall (FQH) state in bulk three dimensional isotropic (not layered) materials.
We find that a FQH state can exist at low densities only if it is accompanied
by a staging transition in which the electrons re-organize themselves in
layers, perpendicular to the magnetic field, at distances of order the magnetic
length apart. The Hartree energy associated to the staging transition is
off-set by the correlation Fock energy of the 3D FQH state. We obtain the phase
diagram of bulk electrons in a magnetic field subject to Coulomb interactions
as a function of carrier density and lattice constant. At very low densities,
the 3D FQH state exhibits a transition to a 3D Wigner crystal state stabilized
by phonon correlations
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