94,654 research outputs found
Density-Dependent Synthetic Gauge Fields Using Periodically Modulated Interactions
We show that density-dependent synthetic gauge fields may be engineered by
combining periodically modu- lated interactions and Raman-assisted hopping in
spin-dependent optical lattices. These fields lead to a density- dependent
shift of the momentum distribution, may induce superfluid-to-Mott insulator
transitions, and strongly modify correlations in the superfluid regime. We show
that the interplay between the created gauge field and the broken sublattice
symmetry results, as well, in an intriguing behavior at vanishing interactions,
characterized by the appearance of a fractional Mott insulator.Comment: 5 pages, 5 figure
Phonon anomalies in pure and underdoped R{1-x}K{x}Fe{2}As{2} (R = Ba, Sr) investigated by Raman light scattering
We present a detailed temperature dependent Raman light scattering study of
optical phonons in Ba{1-x}K{x}Fe{2}As{2} (x ~ 0.28, superconducting Tc ~ 29 K),
Sr{1-x}K{x}Fe{2}As{2} (x ~ 0.15, Tc ~ 29 K) and non-superconducting
BaFe{2}As{2} single crystals. In all samples we observe a strong continuous
narrowing of the Raman-active Fe and As vibrations upon cooling below the
spin-density-wave transition Ts. We attribute this effect to the opening of the
spin-density-wave gap. The electron-phonon linewidths inferred from these data
greatly exceed the predictions of ab-initio density functional calculations
without spin polarization, which may imply that local magnetic moments survive
well above Ts. A first-order structural transition accompanying the
spin-density-wave transition induces discontinuous jumps in the phonon
frequencies. These anomalies are increasingly suppressed for higher potassium
concentrations. We also observe subtle phonon anomalies at the superconducting
transition temperature Tc, with a behavior qualitatively similar to that in the
cuprate superconductors.Comment: 5 pages, 6 figures, accepted versio
A new constant-pressure molecular dynamics method for finite system
In this letter, by writing the volume as a function of coordinates of atoms,
we present a new constant-pressure molecular dynamics method with parameters
free. This method is specially appropriate for the finite system in which the
periodic boundary condition does not exist. Simulations on the carbon nanotube
and the Ni nanoparticle clearly demonstrate the validity of the method. By
using this method, one can easily obtain the equation of states for the finite
system under the external pressure.Comment: RevTex, 5 pages, 3 figures, submitted to Phys. Rev. Let
Many-Body Approximation Scheme Beyond GW
We explore the combination of the extended dynamical mean field theory
(EDMFT) with the GW approximation (GWA); the former sums the local
contributions to the self-energies to infinite order in closed form and the
latter handles the non-local ones to lowest order. We investigate the different
levels of self-consistency that can be implemented within this method by
comparing to the exact QMC solution of a finite-size model Hamiltonian. We find
that using the EDMFT solution for the local self-energies as input to the GWA
for the non-local self-energies gives the best result.Comment: 4 pages, 8 figure
Landau-Zener-Stuckelberg interference in a multi-anticrossing system
We propose a universal analytical method to study the dynamics of a
multi-anticrossing system subject to driving by one single large-amplitude
triangle pulse, within its time scales smaller than the dephasing time. Our
approach can explain the main features of the Landau-Zener-Stuckelberg
interference patterns recently observed in a tripartite system [Nature
Communications 1:51 (2010)]. In particular, we focus on the effects of the size
of anticrossings on interference and compare the calculated interference
patterns with numerical simulations. In addition, Fourier transform of the
patterns can extract information on the energy level spectrum.Comment: 6 pages, 5 figure
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