2,512 research outputs found
Momentum-resolved tunneling between Luttinger liquids
We study tunneling between two nearby cleaved edge quantum wires in a
perpendicular magnetic field. Due to Coulomb forces between electrons, the
wires form a strongly-interacting pair of Luttinger liquids. We calculate the
low-temperature differential tunneling conductance, in which singular features
map out the dispersion relations of the fractionalized quasiparticles of the
system. The velocities of several such spin-charge separated excitations can be
explicitly observed. Moreover, the proposed measurement directly demonstrates
the splintering of the tunneling electrons into a multi-particle continuum of
these quasiparticles, carrying separately charge from spin. A variety of
corrections to the simple Luttinger model are also discussed.Comment: 4 pages, 5 figures (1 in color
Stability of the Bragg glass phase in a layered geometry
We study the stability of the dislocation-free Bragg glass phase in a layered
geometry consisting of coupled parallel planes of d=1+1 vortex lines lying
within each plane, in the presence of impurity disorder. Using renormalization
group, replica variational calculations and physical arguments we show that at
temperatures the 3D Bragg glass phase is always stable for weak
disorder. It undergoes a weakly first order transition into a decoupled 2D
vortex glass upon increase of disorder.Comment: RevTeX. Submitted to EP
Diffusion of Dirac fermions across a topological merging transition in two dimensions
A continuous deformation of a Hamiltonian possessing at low energy two Dirac
points of opposite chiralities can lead to a gap opening by merging of the two
Dirac points. In two dimensions, the critical Hamiltonian possesses a
semi-Dirac spectrum: linear in one direction but quadratic in the other. We
study the transport properties across such a transition, from a Dirac
semi-metal through a semi-Dirac phase towards a gapped phase. Using both a
Boltzmann approach and a diagrammatic Kubo approach, we describe the
conductivity tensor within the diffusive regime. In particular, we show that
both the anisotropy of the Fermi surface and the Dirac nature of the
eigenstates combine to give rise to anisotropic transport times, manifesting
themselves through an unusual matrix self-energy.Comment: 15 pages, 14 figure
Dephasing due to nonstationary 1/f noise
Motivated by recent experiments with Josephson qubits we propose a new
phenomenological model for 1/f noise due to collective excitations of
interacting defects in the qubit's environment. At very low temperatures the
effective dynamics of these collective modes are very slow leading to
pronounced non-Gaussian features and nonstationarity of the noise. We analyze
the influence of this noise on the dynamics of a qubit in various regimes and
at different operation points. Remarkable predictions are absolute time
dependences of a critical coupling and of dephasing in the strong coupling
regime.Comment: 4 pages, 2 figures, to be published in the proceedings of the Vth
Rencontres de Moriond in Mesoscopic Physic
An exactly soluble noisy traveling wave equation appearing in the problem of directed polymers in a random medium
We calculate exactly the velocity and diffusion constant of a microscopic
stochastic model of evolving particles which can be described by a noisy
traveling wave equation with a noise of order . Our model can be
viewed as the infinite range limit of a directed polymer in random medium with
sites in the transverse direction. Despite some peculiarities of the
traveling wave equations in the absence of noise, our exact solution allows us
to test the validity of a simple cutoff approximation and to show that, in the
weak noise limit, the position of the front can be completely described by the
effect of the noise on the first particle.Comment: 5 page
Immune Influence on Adult Neural Stem Cell Regulation and Function
Neural stem cells (NSCs) lie at the heart of central nervous system development and repair, and deficiency or dysregulation of NSCs or their progeny can have significant consequences at any stage of life. Immune signaling is emerging as one of the influential variables that define resident NSC behavior. Perturbations in local immune signaling accompany virtually every injury or disease state, and signaling cascades that mediate immune activation, resolution, or chronic persistence influence resident stem and progenitor cells. Some aspects of immune signaling are beneficial, promoting intrinsic plasticity and cell replacement, while others appear to inhibit the very type of regenerative response that might restore or replace neural networks lost in injury or disease. Here we review known and speculative roles that immune signaling plays in the postnatal and adult brain, focusing on how environments encountered in disease or injury may influence the activity and fate of endogenous or transplanted NSCs
Continuous atom laser with Bose-Einstein condensates involving three-body interactions
We demonstrate, through numerical simulations, the emission of a coherent
continuous matter wave of constant amplitude from a Bose-Einstein Condensate in
a shallow optical dipole trap. The process is achieved by spatial control of
the variations of the scattering length along the trapping axis, including
elastic three body interactions due to dipole interactions. In our approach,
the outcoupling mechanism are atomic interactions and thus, the trap remains
unaltered. We calculate analytically the parameters for the experimental
implementation of this CW atom laser.Comment: 11 pages, 4 figure
Dephasing by a nonstationary classical intermittent noise
We consider a new phenomenological model for a classical
intermittent noise and study its effects on the dephasing of a two-level
system. Within this model, the evolution of the relative phase between the
states is described as a continuous time random walk (CTRW). Using
renewal theory, we find exact expressions for the dephasing factor and identify
the physically relevant various regimes in terms of the coupling to the noise.
In particular, we point out the consequences of the non-stationarity and
pronounced non-Gaussian features of this noise, including some new anomalous
and aging dephasing scenarii.Comment: Submitted to Phys. Rev.
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