2,826 research outputs found
Tunneling effect on composite fermion pairing state in bilayer quantum Hall system
We discuss the composite fermion pairing state in bilayer quantum Hall
systems. After the evaluation of the range of the inter-layer separation in
which the quantum Hall state is stabilized, we discuss the effect of
inter-layer tunneling on the composite fermion pairing state at \nu=1/2. We
show that there is a cusp at the transition point between the Halperin (3,3,1)
state and the Pfaffian state.Comment: 6 pages, 4 figures, accepted for publication in Phys. Rev.
Theory of Incompressible States in a Narrow Channel
We report on the properties of a system of interacting electrons in a narrow
channel in the quantum Hall effect regime. It is shown that an increase in the
strength of the Coulomb interaction causes abrupt changes in the width of the
charge-density profile of translationally invariant states. We derive a phase
diagram which includes many of the stable odd-denominator states as well as a
novel fractional quantum Hall state at lowest half-filled Landau level. The
collective mode evaluated at the half-filled case is strikingly similar to that
for an odd-denominator fractional quantum Hall state.Comment: 4 pages, REVTEX, and 4 .ps file
Parity Effect in a Small Superconducting Particle
Matveev and Larkin calculated the parity effect on the ground state energy of
a small superconducting particle in the regimes where the mean level spacing is
either large or small compared to the bulk gap. We perform a numerical
calculation which extends their results into the intermediate regime, where the
level spacing is of the same order as the bulk gap.Comment: 6 LaTeX pages, including 2 EPS figures; corrected reference and
spellin
Spin phase diagram of the nu_e=4/11 composite fermion liquid
Spin polarization of the "second generation" nu_e=4/11 fractional quantum
Hall state (corresponding to an incompressible liquid in a one-third-filled
composite fermion Landau level) is studied by exact diagonalization. Spin phase
diagram is determined for GaAs structures of different width and electron
concentration. Transition between the polarized and partially unpolarized
states with distinct composite fermion correlations is predicted for realistic
parameters.Comment: 5 pages, 3 figure
Tuning of the Gap in a Laughlin-Bychkov-Rashba Incompressible Liquid
We report on our investigation of the influence of Bychkov-Rashba spin-orbit
interaction (SOI) on the incompressible Laughlin state. We find that
experimentally obtainable values of the spin-orbit coupling strength can induce
as much as a 25% increase in the quasiparticle-quasihole gap Eg at low magnetic
fields in InAs, thereby increasing the stability of the liquid state. The
SOI-modulated enhancement of Eg is also significant for filling factors 1/5 and
1/7, where the FQH state is usually weak. This raises the intriguing
possibility of tuning, via the SO coupling strength, the liquid to solid
transition to much lower densities.Comment: 4 pages, 3 figure
Can Induced Theta Vacua be Created in Heavy Ion Collisions?
The development of the early Universe is a remarkable laboratory for the
study of most nontrivial properties of particle physics. What is more
remarkable is the fact that these phenomena at the QCD scale can be, in
principle, experimentally tested in heavy ion collisions. We expect that, in
general, an arbitrary theta-state would be created in the heavy ion collisions,
similar to the creation of the disoriented chiral condensate with an arbitrary
isospin direction. It should be a large domain with a wrong
orientation. We test this idea numerically in a simple model where we study the
evolution of the phases of the chiral condensates in QCD with two quark flavors
with non-zero theta-parameter. We see the formation of a non-zero theta-vacuum
with the formation time of the order of seconds. This result will
have important implications for a possible axion search experiment at RHIC.Comment: 4 pages, 3 figures, Latex, Discussion of experimental signatures
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Optical-conductivity sum rule in cuprates and unconventional charge density waves: a short review
We begin with an overview of the experimental results for the temperature and
doping dependences of the optical-conductivity spectral weight in cuprate
superconductors across the whole phase diagram. Then we discuss recent attempts
to explain the observed behavior of the spectral weight using reduced and full
models with unconventional charge-density waves.Comment: 17 pages, RevTeX4, 4 EPS figures; Invited paper for a special issue
of Low Temperature Physics dedicated to the 20th anniversary of HTS
Response Function of the Fractional Quantized Hall State on a Sphere II: Exact Diagonalization
We study the excitation spectra and the dynamical structure factor of quantum
Hall states in a finite size system through exact diagonalization. Comparison
is made between the numerical results so obtained and the analytic results
obtained from a modified RPA in the preceding companion paper. We find good
agreement between the results at low energies.Comment: 22 pages (REVTeX 3.0). 10 figures available on request. Complete
postscript file (including figures) for this paper are available on the World
Wide Web at http://cmtw.harvard.edu/~simon/ ; Preprint number HU-CMT-94S0
Spin textures, screening and excitations in dirty quantum Hall ferromagnets
We study quantum Hall ferromagnets in the presence of a random electrostatic
impurity potential. Describing these systems with a classical non-linear sigma
model and using analytical estimates supported by results from numerical
simulations, we examine the nature of the ground state as a function of
disorder strength, , and deviation, , of the average Landau
level filling factor from unity. Screening of an impurity potential requires
distortions of the spin configuration, and in the absence of Zeeman coupling
there is a disorder-driven, zero-temperature phase transition from a
ferromagnet at small and to a spin glass at larger
or . We examine ground-state response functions and
excitations.Comment: 4 pages, 3 figure
Fluctuation-Driven Quantum Phase Transitions in Clean Itinerant Ferromagnets
The quantum phase transition in clean itinerant ferromagnets is analyzed. It
is shown that soft particle-hole modes invalidate Hertz's mean-field theory for
. A renormalized mean-field theory predicts a fluctuation-induced
first order transition for , whose stability is analyzed by
renormalization group techniques. Depending on microscopic parameter values,
the first order transition can be stable, or be pre-empted by a
fluctuation-induced second order transition. The critical behavior at the
latter is determined. The results are in agreement with recent experiments.Comment: 4 pp., REVTeX, no figs; final version as publishe
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