4,387 research outputs found
s-wave pairing in the optimally-doped LaO0.5F0.5BiS2 superconductor
We report on the magnetic and superconducting properties of LaO0.5F0.5BiS2 by
means of zero- (ZF) and transverse-field (TF) muon-spin spectroscopy
measurements (uSR). Contrary to previous results on iron-based superconductors,
measurements in zero field demonstrate the absence of magnetically ordered
phases. TF-uSR data give access to the superfluid density, which shows a marked
2D character with a dominant s-wave temperature behavior. The field dependence
of the magnetic penetration depth confirms this finding and further suggests
the presence of an anisotropic superconducting gap
Nonlinear dynamics of large amplitude dust acoustic shocks and solitary pulses in dusty plasmas
We present a fully nonlinear theory for dust acoustic (DA) shocks and DA
solitary pulses in a strongly coupled dusty plasma, which have been recently
observed experimentally by Heinrich et al. [Phys. Rev. Lett. 103, 115002
(2009)], Teng et al. [Phys. Rev. Lett. 103, 245005 (2009)], and Bandyopadhyay
et al. [Phys. Rev. Lett. 101, 065006 (2008)]. For this purpose, we use a
generalized hydrodynamic model for the strongly coupled dust grains, accounting
for arbitrary large amplitude dust number density compressions and potential
distributions associated with fully nonlinear nonstationary DA waves.
Time-dependent numerical solutions of our nonlinear model compare favorably
well with the recent experimental works (mentioned above) that have reported
the formation of large amplitude non-stationary DA shocks and DA solitary
pulses in low-temperature dusty plasma discharges.Comment: 9 pages, 4 figures. To be published in Physical Review
Transport through side-coupled double quantum dots: from weak to strong interdot coupling
We report low-temperature transport measurements through a double quantum dot
device in a configuration where one of the quantum dots is coupled directly to
the source and drain electrodes, and a second (side-coupled) quantum dot
interacts electrostatically and via tunneling to the first one. As the interdot
coupling increases, a crossover from weak to strong interdot tunneling is
observed in the charge stability diagrams that present a complex pattern with
mergings and apparent crossings of Coulomb blockade peaks. While the weak
coupling regime can be understood by considering a single level on each dot, in
the intermediate and strong coupling regimes, the multi-level nature of the
quantum dots needs to be taken into account. Surprisingly, both in the strong
and weak coupling regimes, the double quantum dot states are mainly localized
on each dot for most values of the parameters. Only in an intermediate coupling
regime the device presents a single dot-like molecular behavior as the
molecular wavefunctions weight is evenly distributed between the quantum dots.
At temperatures larger than the interdot coupling energy scale, a loss of
coherence of the molecular states is observed.Comment: 9 pages, 5 figure
Effect of Disorder on the Quantum Coherence in Mesoscopic Wires
We present phase coherence time measurements in quasi-one-dimensional
mesoscopic wires made from high mobility two-dimensional electron gas. By
implanting gallium ions into a GaAs/AlGaAs heterojunction we are able to vary
the diffusion coefficient over 2 orders of magnitude. We show that in the
diffusive limit, the decoherence time follows a power law as a function of
diffusion coefficient as expected by theory. When the disorder is low enough so
that the samples are semi-ballistic, we observe a new and unexpected regime in
which the phase coherence time is independent of disorder. In addition, for all
samples the temperature dependence of the phase coherence time follows a power
law down to the lowest temperatures without any sign of saturation and strongly
suggests that the frequently observed low temperature saturation is not
intrinsic.Comment: 4 pages, 4 figure
Muons as Local Probes of Three-body Correlations in the Mixed State of Type-II Superconductors
The vortex glass state formed by magnetic flux lines in a type-II
superconductor is shown to possess non-trivial three-body correlations. While
such correlations are usually difficult to measure in glassy systems, the
magnetic fields associated with the flux vortices allow us to probe these via
muon-spin rotation measurements of the local field distribution. We show via
numerical simulations and analytic calculations that these observations provide
detailed microscopic insight into the local order of the vortex glass and more
generally validate a theoretical framework for correlations in glassy systems.Comment: 4+ pages, high-quality figures available on reques
Kondo physics in the algebraic spin liquid
We study Kondo physics in the algebraic spin liquid, recently proposed to
describe [Phys. Rev. Lett. {\bf 98}, 117205 (2007)].
Although spin dynamics of the algebraic spin liquid is described by massless
Dirac fermions, this problem differs from the Pseudogap Kondo model, because
the bulk physics in the algebraic spin liquid is governed by an interacting
fixed point where well-defined quasiparticle excitations are not allowed.
Considering an effective bulk model characterized by an anomalous critical
exponent, we derive an effective impurity action in the slave-boson context.
Performing the large- analysis with a spin index , we
find an impurity quantum phase transition from a decoupled local-moment state
to a Kondo-screened phase. We evaluate the impurity spin susceptibility and
specific heat coefficient at zero temperature, and find that such responses
follow power-law dependencies due to the anomalous exponent of the algebraic
spin liquid. Our main finding is that the Wilson's ratio for the magnetic
impurity depends strongly on the critical exponent in the zero temperature
limit. We propose that the Wilson's ratio for the magnetic impurity may be one
possible probe to reveal criticality of the bulk system
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