2,602 research outputs found
Dynamics of compressible edge and bosonization
We work out the dynamics of the compressible edge of the quantum Hall system
based on the electrostatic model of Chklovskii et al.. We introduce a
generalized version of Wen's hydrodynamic quantization approach to the dynamics
of sharp edge and rederive Aleiner and Glazman's earlier result of multiple
density modes. Bosonic operators of density excitations are used to construct
fermions at the interface of the compressible and incompressible region. We
also analyze the dynamics starting with the second-quantized Hamiltonian in the
lowest Landau level and work out the time development of density operators.
Contrary to the hydrodynamic results, the density modes are strongly coupled.
We argue that the coupling suppresses the propagation of all acoustic modes,
and that the excitations with large wavevectors are subject to decay due to
coupling to the dissipative acoustic modes.A possible correction to the
tunneling density of states is discussed.Comment: 7 pages, Revtex, 1 figur
Neutrino-nucleus interactions at low energies within Fermi-liquid theory
Cross sections are calculated for neutrino scattering off heavy nuclei at
energies below 50 MeV. The theory of Fermi liquid is applied to estimate the
rate of neutrino-nucleon elastic and inelastic scattering in a nuclear medium
in terms of dynamic form factors. The cross sections, obtained here in a rather
simple way, are in agreement with the results of the other much more
sophisticated nuclear models. A background rate from the solar neutrino
interactions within a large Ge detector is estimated in the above-mentioned
approach. The knowledge of the rate is in particular rather important for
new-generation large-scale neutrino experiments.Comment: 9 pages, 6 figure
Single-particle and collective excitations in a charged Bose gas at finite temperature
The main focus of this work is on the predictions made by the dielectric
formalism in regard to the relationship between single-particle and collective
excitation spectra in a gas of point-like charged bosons at finite temperature
below the critical region of Bose-Einstein condensation. Illustrative
numerical results at weak coupling () are presented within the Random
Phase Approximation. We show that within this approach the single-particle
spectrum forms a continuum extending from the transverse to the longitudinal
plasma mode frequency and leading to a double-peak structure as increases,
whereas the density fluctuation spectrum consists of a single broadening peak.
We also discuss the momentum distribution and the superfluidity of the gas.Comment: 15 pages, 5 figure
Theory of the Optical Conductivity in the Cuprate Superconductors
We present a study of the normal state optical conductivity in the cuprate
superconductors using the nearly antiferromagnetic Fermi liquid (NAFL)
description of the magnetic interaction between their planar quasiparticles. We
find that the highly anisotropic scattering rate in different regions of the
Brillouin zone, both as a function of frequency and temperature, a benchmark of
NAFL theory, leads to an average relaxation rate of the Marginal Fermi Liquid
form for overdoped and optimally doped systems, as well as for underdoped
systems at high temperatures. We carry out numerical calculations of the
optical conductivity for several compounds for which the input spin fluctuation
parameters are known. Our results, which are in agreement with experiment on
both overdoped and optimally doped systems, show that NAFL theory explains the
anomalous optical behavior found in these cuprate superconductors.Comment: REVTEX file, 8 PostScript figure
Frequency dependent polarizability of small metallic grains
We study the dynamic electronic polarizability of a single nano-scale
spherical metallic grain using quantum mechanical approach. We introduce the
model for interacting electrons bound in the grain allowing us numerically to
calculate the frequency dependence of the polarizability of grains of different
sizes. We show that within this model the main resonance peak corresponding to
the surface plasmon mode is blue-shifted and some minor secondary resonances
above and below the main peak exist. We study the behavior of blue shift as a
function of grain size and compare our findings with the classical
polarizability and with other results in the literature.Comment: 8 pages, 3 figure
Frequency spectrum of gravitational radiation from global hydromagnetic oscillations of a magnetically confined mountain on an accreting neutron star
Recent time-dependent, ideal-magnetohydrodynamic (ideal-MHD) simulations of
polar magnetic burial in accreting neutron stars have demonstrated that stable,
magnetically confined mountains form at the magnetic poles, emitting
gravitational waves at (stellar spin frequency) and . Global
MHD oscillations of the mountain, whether natural or stochastically driven, act
to modulate the gravitational wave signal, creating broad sidebands (full-width
half-maximum ) in the frequency spectrum around and . The oscillations can enhance the signal-to-noise ratio achieved by a
long-baseline interferometer with coherent matched filtering by up to 15 per
cent, depending on where lies relative to the noise curve minimum.
Coherent, multi-detector searches for continuous waves from nonaxisymmetric
pulsars should be tailored accordingly.Comment: 4 figures, accepted for publication in Ap
STM/STS Study on 4a X 4a Electronic Charge Order and Inhomogeneous Pairing Gap in Superconducting Bi2Sr2CaCu2O8+d
We performed STM/STS measurements on underdoped Bi2212 crystals with doping
levels p ~ 0.11, ~ 0.13 and ~ 0.14 to examine the nature of the nondispersive
4a X 4a charge order in the superconducting state at T << Tc. The charge order
appears conspicuously within the pairing gap, and low doping tends to favor the
charge order. We point out the possibility that the 4a X 4a charge order will
be dynamical in itself, and pinned down over regions with effective pinning
centers. The pinned 4a X 4a charge order is closely related to the spatially
inhomogeneous pairing gap structure, which has often been reported in STS
measurements on high-Tc cuprates.Comment: 12 pages, 16 figures, to be published in Phys. Rev.
Single-particle and collective excitations in quantum wires made up of vertically stacked quantum dots: Zero magnetic field
We report on the theoretical investigation of the elementary electronic
excitations in a quantum wire made up of vertically stacked self-assembled
InAs/GaAs quantum dots. The length scales (of a few nanometers) involved in the
experimental setups prompt us to consider an infinitely periodic system of
two-dimensionally confined (InAs) quantum dot layers separated by GaAs spacers.
The the Bloch functions and the Hermite functions together characterize the
whole system. We then make use of the Bohm-Pines' (full) random-phase
approximation in order to derive a general nonlocal, dynamic dielectric
function. Thus developed theoretical framework is then specified to work within
a (lowest miniband and) two-subband model that enables us to scrutinize the
single-particle as well as collective responses of the system. We compute and
discuss the behavior of the eigenfunctions, band-widths, density of states,
Fermi energy, single-particle and collective excitations, and finally size up
the importance of studying the inverse dielectric function in relation with the
quantum transport phenomena. It is remarkable to notice how the variation in
the barrier- and well-widths can allow us to tailor the excitation spectrum in
the desired energy range. Given the advantage of the vertically stacked quantum
dots over the planar ones and the foreseen applications in the single-electron
devices and in the quantum computation, it is quite interesting and important
to explore the electronic, optical, and transport phenomena in such systems
Dust ion-acoustic shocks in quantum dusty pair-ion plasmas
The formation of dust ion-acoustic shocks (DIASs) in a four-component quantum
plasma whose constituents are electrons, both positive and negative ions and
immobile charged dust grains, is studied. The effects of both the dissipation
due to kinematic viscosity and the dispersion caused by the charge separation
as well as the quantum tunneling due to the Bohm potential are taken into
account. The propagation of small but finite amplitude dust ion-acoustic waves
(DIAWs) is governed by the Korteweg-de Vries-Burger (KdVB) equation which
exhibits both oscillatory and monotonic shocks depending not only on the
viscosity parameters, but also on the quantum parameter H (the ratio of the
electron plasmon to the electron Fermi energy) and the positive to negative ion
density ratio. Large amplitude stationary shocks are recovered for a Mach
number exceeding its critical value. Unlike the small amplitude shocks, quite a
smaller value of the viscosity parameter, H and the density ratio may lead to
the large amplitude monotonic shock strucutres. The results could be of
importance in astrophysical and laser produced plasmas.Comment: 15 pages, 5 figure
The rigidity of crystalline color superconducting quark matter
We calculate the shear modulus of crystalline color superconducting quark
matter, showing that this phase of dense, but not asymptotically dense,
three-flavor quark matter responds to shear stress like a very rigid solid. To
evaluate the shear modulus, we derive the low energy effective Lagrangian that
describes the phonons that originate from the spontaneous breaking of
translation invariance by the spatial modulation of the gap parameter .
These massless bosons describe space- and time-dependent fluctuations of the
crystal structure and are analogous to the phonons in ordinary crystals. The
coefficients of the spatial derivative terms of the phonon effective Lagrangian
are related to the elastic moduli of the crystal; the coefficients that encode
the linear response of the crystal to a shearing stress define the shear
modulus. We analyze the two particular crystal structures which are
energetically favored over a wide range of densities, in each case evaluating
the phonon effective action and the shear modulus up to order in a
Ginzburg-Landau expansion, finding shear moduli which are 20 to 1000 times
larger than those of neutron star crusts. The crystalline color superconducting
phase has long been known to be a superfluid -- by picking a phase its order
parameter breaks the quark-number symmetry spontaneously. Our results
demonstrate that this superfluid phase of matter is at the same time a rigid
solid. We close with a rough estimate of the pinning force on the rotational
vortices which would be formed embedded within this rigid superfluid upon
rotation. Our results raise the possibility that (some) pulsar glitches could
originate within a quark matter core deep within a neutron star.Comment: 38 pages, 5 figures. v3. Two new paragraphs in Section V
(Conclusion); some additional small changes. A paragraph discussing
supercurrents added in Section I (Introduction). Version to appear in Phys.
Rev.
- …