21,012 research outputs found
Antiferromagnetic Order in Pauli Limited Unconventional Superconductors
We develop a theory of the coexistence of superconductivity (SC) and
antiferromagnetism (AFM) in CeCoIn5. We show that in Pauli-limited nodal
superconductors the nesting of the quasi-particle pockets induced by Zeeman
pair-breaking leads to incommensurate AFM with the moment normal to the field.
We compute the phase diagram and find a first order transition to the normal
state at low temperatures, absence of normal state AFM, and coexistence of SC
and AFM at high fields, in agreement with experiments. We also predict the
existence of a new double-Q magnetic phase
Electronic and thermoelectric properties of Fe2VAl: The role of defects and disorder
Using first-principles calculations, we show that Fe2VAl is an indirect band
gap semiconductor. Our calculations reveal that its, sometimes assigned,
semimetallic character is not an intrinsic property but originates from the
antisite defects and site disorder, which introduce localized ingap and
resonant states changing the electronic properties close to band gap. These
states negatively affect the thermopower S and power factor PF=S^2\sigma,
decreasing the good thermoelectric performance of intrinsic Fe2VAl.Comment: 4 pages, 6 figures, thermoelectric properties, electronic structure
and transport properties, effect of antisite defects and disorder on
electronic and transport propertie
Analytic structure of Bloch functions for linear molecular chains
This paper deals with Hamiltonians of the form H=-{\bf \nabla}^2+v(\rr),
with v(\rr) periodic along the direction, . The
wavefunctions of are the well known Bloch functions
\psi_{n,\lambda}(\rr), with the fundamental property
and
. We give the generic analytic structure
(i.e. the Riemann surface) of \psi_{n,\lambda}(\rr) and their corresponding
energy, , as functions of . We show that
and are different branches of two multi-valued
analytic functions, and , with an essential
singularity at and additional branch points, which are generically
of order 1 and 3, respectively. We show where these branch points come from,
how they move when we change the potential and how to estimate their location.
Based on these results, we give two applications: a compact expression of the
Green's function and a discussion of the asymptotic behavior of the density
matrix for insulating molecular chains.Comment: 13 pages, 11 figure
On the convergence of second order spectra and multiplicity
Let A be a self-adjoint operator acting on a Hilbert space. The notion of
second order spectrum of A relative to a given finite-dimensional subspace L
has been studied recently in connection with the phenomenon of spectral
pollution in the Galerkin method. We establish in this paper a general
framework allowing us to determine how the second order spectrum encodes
precise information about the multiplicity of the isolated eigenvalues of A.
Our theoretical findings are supported by various numerical experiments on the
computation of inclusions for eigenvalues of benchmark differential operators
via finite element bases.Comment: 22 pages, 2 figures, 4 tables, research paper
Rate of Convergence in Nonlinear Hartree Dynamics with Factorized Initial Data
The mean field dynamics of an -particle weekly interacting Boson system
can be described by the nonlinear Hartree equation. In this paper, we present
estimates on the 1/N rate of convergence of many-body Schr\"{o}dinger dynamics
to the one-body nonlinear Hartree dynamics with factorized initial data with
two-body interaction potential in .Comment: AMS LaTex, 21 page
Angular Momentum Transport in Particle and Fluid Disks
We examine the angular momentum transport properties of disks composed of
macroscopic particles whose velocity dispersions are externally enhanced
(``stirred''). Our simple Boltzmann equation model serves as an analogy for
unmagnetized fluid disks in which turbulence may be driven by thermal
convection. We show that interparticle collisions in particle disks play the
same role as fluctuating pressure forces and viscous dissipation in turbulent
disks: both transfer energy in random motions associated with one direction to
those associated with another, and convert kinetic energy into heat. The
direction of angular momentum transport in stirred particle and fluid disks is
determined by the direction of external stirring and by the properties of the
collision term in the Boltzmann equation (or its analogue in the fluid
problem). In particular, our model problem yields inward transport for
vertically or radially stirred disks, provided collisions are suitably
inelastic; the transport is outwards in the elastic limit. Numerical
simulations of hydrodynamic turbulence driven by thermal convection find inward
transport; this requires that fluctuating pressure forces do little to no work,
and is analogous to an externally stirred particle disk in which collisions are
highly inelastic.Comment: 15 pages; final version accepted by ApJ; minor changes, some
clarificatio
Particle Propagator of Spin Calogero-Sutherland Model
Explicit-exact expressions for the particle propagator of the spin 1/2
Calogero-Sutherland model are derived for the system of a finite number of
particles and for that in the thermodynamic limit. Derivation of the expression
in the thermodynamic limit is also presented in detail. Combining this result
with the hole propagator obtained in earlier studies, we calculate the spectral
function of the single particle Green's function in the full range of the
energy and momentum space. The resultant spectral function exhibits power-law
singularity characteristic to correlated particle systems in one dimension.Comment: 43 pages, 6 figure
Dynamical magnetic susceptibility in the lamellar cobaltate superconductor Na_xCoO_2H_2O
We systematically analyze the influence of the superconducting gap symmetry
and the electronic structure on the dynamical spin susceptibility in
superconducting Na_xCoO_2H_2O within a three different models: the
single a_{1g}-band model with nearest-neighbor hoppings, the realistic
three-band t_{2g}-model with, and without e'_g pockets present at the Fermi
surface. We show that the magnetic response in the normal state is dominated by
the incommensurate antiferromagnetic spin density wave fluctuations at large
momenta in agreement with experimental temperature dependence of the
spin-lattice relaxation rate. Also, we demonstrate that the presence or the
absence of the e'_g-pockets at the Fermi surface does not affect significantly
this conclusion. In the superconducting state our results for d_{x^2-y^2}- or
d_{xy}-wave symmetries of the superconducting order parameter are consistent
with experimental data and exclude nodeless -wave
symmetry. We further point out that the spin-resonance peak proposed earlier is
improbable for the realistic band structure of Na_xCoO_2H_2O.
Moreover, even if present the resonance peak is confined to the
antiferromagnetic wave vector and disappears away from it.Comment: Published version, PACS: 74.70.-b; 75.40.Gb; 74.20.Rp; 74.25.J
Non-equilibrium spin polarization effects in spin-orbit coupling system and contacting metallic leads
We study theoretically the current-induced spin polarization effect in a
two-terminal mesoscopic structure which is composed of a semiconductor
two-dimensional electron gas (2DEG) bar with Rashba spin-orbit (SO) interaction
and two attached ideal leads. The nonequilibrium spin density is calculated by
solving the scattering wave functions explicitly within the ballistic transport
regime. We found that for a Rashba SO system the electrical current can induce
spin polarization in the SO system as well as in the ideal leads. The induced
polarization in the 2DEG shows some qualitative features of the intrinsic spin
Hall effect. On the other hand, the nonequilibrium spin density in the ideal
leads, after being averaged in the transversal direction, is independent of the
distance measured from the lead/SO system interface, except in the vicinity of
the interface. Such a lead polarization effect can even be enhanced by the
presence of weak impurity scattering in the SO system and may be detectable in
real experiments.Comment: 6 pages,5 figure
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