1,394 research outputs found

    Phonon-mediated electron spin phase diffusion in a quantum dot

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    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

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    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

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    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

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    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

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    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

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    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

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    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

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    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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