286 research outputs found
Edge electron states for quasi-one-dimensional organic conductors in the magnetic-field-induced spin-density-wave phases
We develop a microscopic picture of the electron states localized at the
edges perpendicular to the chains in the Bechgaard salts in the quantum Hall
regime. In a magnetic-field-induced spin-density-wave state (FISDW)
characterized by an integer N, there exist N branches of chiral gapless edge
excitations. Localization length is much longer and velocity much lower for
these states than for the edge states parallel to the chains. We calculate the
contribution of these states to the specific heat and propose a time-of-flight
experiment to probe the propagating edge modes directly.Comment: 4 pages, 2 figures. V.2: Minor changes to the final version published
in PR
A study on correlation effects in two dimensional topological insulators
We investigate correlation effects in two dimensional topological insulators
(TI). In the first part, we discuss finite size effects for interacting systems
of different sizes in a ribbon geometry. For large systems, there are two pairs
of well separated massless modes on both edges. For these systems, we analyze
the finite size effects using a standard bosonization approach. For small
systems, where the edge states are massive Dirac fermions, we use the
inhomogeneous dynamical mean field theory (DMFT) combined with iterative
perturbation theory as an impurity solver to study interaction effects. We show
that the finite size gap in the edge states is renormalized for weak
interactions, which is consistent with a Fermi-liquid picture for small size
TIs. In the second part, we investigate phase transitions in finite size TIs at
zero temperature focusing on the effects of possible inter-edge Umklapp
scattering for the edge states within the inhomogeneous DMFT using the
numerical renormalization group. We show that correlation effects are
effectively stronger near the edge sites because the coordination number is
smaller than in the bulk. Therefore, the localization of the edge states around
the edge sites, which is a fundamental property in TIs, is weakened for strong
coupling strengths. However, we find no signs for "edge Mott insulating states"
and the system stays in the topological insulating state, which is
adiabatically connected to the non-interacting state, for all interaction
strengths smaller than the critical value. Increasing the interaction further,
a nearly homogeneous Mott insulating state is stabilized.Comment: 20 page
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Theory of Resonance Influence of Sawtooth Crashes on Ions with Large Orbit Width
The role of resonances in the sawtooth-crash-induced redistribution of fast ions is investigated. In particular, the conditions of wave-particle resonant interaction in the presence of the equilibrium electric field and the mode rotation are obtained, and effects of sawteeth on the resonant particles with arbitrary width of non-perturbed orbits are studied. It is found that resonances play the dominant role in the transport of ions having sufficiently high energy. It is shown that the resonance regions may overlap, in which case the resonant particles may constitute the main fraction of the fast ion population in the sawtooth mixing region. The behavior of the resonant particles is studied both by constructing a Poincaré map and analytically, by means of the adiabatic invariant derived in this paper and calculation of the characteristic frequencies of the particle motion
Ideal MHD theory of low-frequency Alfven waves in the H-1 Heliac
A part analytical, part numerical ideal MHD analysis of low-frequency Alfven
wave physics in the H-1 stellarator is given. The three-dimensional,
compressible ideal spectrum for H-1 is presented and it is found that despite
the low beta (approx. 10^-4) of H-1 plasmas, significant Alfven-acoustic
interactions occur at low frequencies. Several quasi-discrete modes are found
with the three-dimensional linearised ideal MHD eigenmode solver CAS3D,
including beta-induced Alfven eigenmode (BAE)- type modes in beta-induced gaps.
The strongly shaped, low-aspect ratio magnetic geometry of H-1 causes CAS3D
convergence difficulties requiring the inclusion of many Fourier harmonics for
the parallel component of the fluid displacement eigenvector even for shear
wave motions. The highest beta-induced gap reproduces large parts of the
observed configurational frequency dependencies in the presence of hollow
temperature profiles
Use of a recombinant human follicle-stimulating hormone:recombinant human luteinizing hormone (r-hFSH:r-hLH) 2:1 combination for controlled ovarian stimulation during assisted reproductive technology treatment: A real-world study of routine practice in the Russian Federation
Two observational studies in the Russian Federation described patient demographics/clinical decision for treatment with recombinant human follicle-stimulating hormone:recombinant human luteinizing hormone (r-hFSH:r-hLH) 2:1 combination for ovarian stimulation (OS) during assisted reproductive technology (ART) and outcomes, respectively. The first (prospective) study enrolled 500 patients. After post-hoc regrouping to assign patients to discrete groups, 378 (75.6%) met the local Russian label for an r-hFSH:r-hLH 2:1 combination, 105 (21%) were treated according to other physician preference, and 17 (3.4%) met only the ESHRE Bologna criteria for a poor ovarian response. The clinical pregnancy rate per cycle was 30.4%. A total of 158/175 (90.3%) women achieving clinical pregnancy in the prospective study participated in the second (retrospective) study. The live birth rate per cycle was 25.8%. No new safety concerns were reported. These results support the use of the r-hFSH:r-hLH 2:1 combination in patients with a poor/suboptimal response to OS for ART treatment in the Russian Federation
Quasi-Andreev reflection in inhomogeneous Luttinger liquids
Reflection of charge excitations at the step in the interaction strength in a
Luttinger liquid can be of the Andreev type, even if the interactions are
purely repulsive. The region with stronger repulsion plays the role of a normal
metal in a normal-metal /superconductor junction, whereas the region with
weaker repulsion plays the role of a superconductor. It is shown that this
quasi-Andreev reflection leads to a number of proximity-like effects, including
the local enhancement (suppression) of superconducting fluctuations on the
quasi-normal (quasi-superconducting) side of the step, significant modification
of the local density of states, as well as others. The observable consequences
of these proximity effects are analyzed for the case of single- and
two-particle tunneling from a normal-metal or superconducting tip into an
inhomogeneous Luttinger-liquid wire.Comment: 5 pages, 2 figures (eps
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