1,394 research outputs found

### Phonon-mediated electron spin phase diffusion in a quantum dot

An effective spin relaxation mechanism that leads to electron spin
decoherence in a quantum dot is proposed. In contrast to the common
calculations of spin-flip transitions between the Kramers doublets, we take
into account a process of phonon-mediated fluctuation in the electron spin
precession and subsequent spin phase diffusion. Specifically, we consider
modulations in the longitudinal g-factor and hyperfine interaction induced by
the phonon-assisted transitions between the lowest electronic states. Prominent
differences in the temperature and magnetic field dependence between the
proposed mechanisms and the spin-flip transitions are expected to facilitate
its experimental verification. Numerical estimation demonstrates highly
efficient spin relaxation in typical semiconductor quantum dots.Comment: 5 pages, 1 figur

### Growing length and time scales in a suspension of athermal particles

We simulate a relaxation process of non-brownian particles in a sheared
viscous medium; the small shear strain is initially applied to a system, which
then undergoes relaxation. The relaxation time and the correlation length are
estimated as functions of density, which algebraically diverge at the jamming
density. This implies that the relaxation time can be scaled by the correlation
length using the dynamic critical exponent, which is estimated as 4.6(2). It is
also found that shear stress undergoes power-law decay at the jamming density,
which is reminiscent of critical slowing down

### A Green's function decoupling scheme for the Edwards fermion-boson model

Holes in a Mott insulator are represented by spinless fermions in the
fermion-boson model introduced by Edwards. Although the physically interesting
regime is for low to moderate fermion density the model has interesting
properties over the whole density range. It has previously been studied at
half-filling in the one-dimensional (1D) case by numerical methods, in
particular exact diagonalization and density matrix renormalization group
(DMRG). In the present study the one-particle Green's function is calculated
analytically by means of a decoupling scheme for the equations of motion, valid
for arbitrary density in 1D, 2D and 3D with fairly large boson energy and zero
boson relaxation parameter. The Green's function is used to compute some ground
state properties, and the one-fermion spectral function, for fermion densities
n=0.1, 0.5 and 0.9 in the 1D case. The results are generally in good agreement
with numerical results obtained by DMRG and dynamical DMRG and new light is
shed on the nature of the ground state at different fillings. The Green's
function approximation is sufficiently successful in 1D to justify future
application to the 2D and 3D cases.Comment: 19 pages, 7 figures, final version with updated reference

### Statistical Description of Hydrodynamic Processes in Ionic Melts with taking into account Polarization Effects

Statistical description of hydrodynamic processes for ionic melts is proposed
with taking into account polarization effects caused by the deformation of
external ionic shells. This description is carried out by means of the Zubarev
nonequilibrium statistical operator method, appropriate for investigations of
both strong and weak nonequilibrium processes. The nonequilibrium statistical
operator and the generalized hydrodynamic equations that take into account
polarization processes are received for ionic-polarization model of ionic
molten salts when the nonequilibrium averaged values of densities of ions
number, their momentum, dipole momentum and total energy are chosen for the
reduced description parameters. A spectrum of collective excitations is
investigated within the viscoelastic approximation for ion-polarization model
of ionic melts.Comment: 24 pages, RevTex4.1-format, no figure

### Tuning the Non-local Spin-Spin Interaction between Quantum Dots with a Magnetic Field

We describe a device where the non-local spin-spin interaction between two
quantum dots can be turned on and off and even changed sign with a very small
magnetic field. The setup consists of two quantum dots at the edge of two
two-dimensional electron gases (2DEGs). The quantum dots' spins are coupled
through a RKKY-like interaction mediated by the electrons in the 2DEGs. A small
magnetic field perpendicular to the plane of the 2DEG is used as a tuning
parameter. When the cyclotron radius is commensurate with the interdot
distance, the spin-spin interaction is amplified by a few orders of magnitude.
The sign of the interaction is controlled by finely tuning the magnetic field.
Our setup allows for several dots to be coupled in a linear arrangement and it
is not restricted to nearest-neighbors interaction.Comment: 4 pages, 5 figures. Published versio

### Damping of giant dipole resonance in hot rotating nuclei

The phonon damping model (PDM) is extended to include the effect of angular
momentum at finite temperature. The model is applied to the study of damping of
giant dipole resonance (GDR) in hot and noncollectively rotating spherical
nuclei. The numerical results obtained for Mo88 and Sn106 show that the GDR
width increases with both temperature T and angular momentum M. At T > 4 MeV
and M<= 60 hbar the increase in the GDR width slows down for Sn106, whereas at
M<= 80 hbar the GDR widths in both nuclei nearly saturate. By adopting the
nuclear shear viscosity extracted from fission data at T= 0, it is shown that
the maximal value of the angular momentum for Mo88 and Sn106 should be around
46 and 55 hbar, respectively, so that the universal conjecture for the lower
bound of the specific shear viscosity for all fluids is not violated up to T= 5
MeV.Comment: 19 pages, 6 figures, accepted in Phys. Rev.

### Dynamics of the Free Surface of a Conducting Liquid in a Near-Critical Electric Field

Near-critical behavior of the free surface of an ideally conducting liquid in
an external electric field is considered. Based on an analysis of three-wave
processes using the method of integral estimations, sufficient criteria for
hard instability of a planar surface are formulated. It is shown that the
higher-order nonlinearities do not saturate the instability, for which reason
the growth of disturbances has an explosive character.Comment: 19 page

### Magnetorheological properties of ferrofluids containing clustered particles

A theoretical model is proposed to describe experimental data on the magnetorheological properties of magnetic fluids containing clustered particles consisting of single-domain ferromagnetic nanoparticles distributed in a polymeric shell 80-100 nm in diameter. These fluids combine the sedimentation stability typical of nanodisperse ferrofluids with the high sensitivity of rheological parameters to magnetic fields. The developed model explains the experimentally found long-term rheological relaxation and residual stress that is retained after the medium ceases to flow. © 2013 Pleiades Publishing, Ltd

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