2,409 research outputs found
Quantum oscillations and a non-trivial Berry phase in the noncentrosymmetric superconductor BiPd
We report the measurements of de Haas-van Alphen (dHvA) oscillations in the
noncentrosymmetric superconductor BiPd. Several pieces of a complex multi-sheet
Fermi surface are identified, including a small pocket (frequency 40 T) which
is three dimensional and anisotropic. From the temperature dependence of the
amplitude of the oscillations, the cyclotron effective mass is (
0.1) . Further analysis showed a non-trivial -Berry phase is
associated with the 40 T pocket, which strongly supports the presence of
topological states in bulk BiPd and may result in topological superconductivity
due to the proximity coupling to other bands.Comment: 5 pages, 3 figure
Redefining the performing arts archive
This paper investigates representations of performance and the role of the archive. Notions of record and archive are critically investigated, raising questions about applying traditional archival definitions to the performing arts. Defining the nature of performances is at the root of all difficulties regarding their representation. Performances are live events, so for many people the idea of recording them for posterity is inappropriate. The challenge of creating and curating representations of an ephemeral art form are explored and performance-specific concepts of record and archive are posited. An open model of archives, encouraging multiple representations and allowing for creative reuse and reinterpretation to keep the spirit of the performance alive, is envisaged as the future of the performing arts archive
Neutron Scattering Study of Fluctuating and Static Spin Correlations in the Anisotropic Spin Glass FeTiO
The anisotropic spin glass transition, in which spin freezing is observed
only along the c-axis in pseudobrookite FeTiO, has long been perplexing
because the Fe moments (d) are expected to be isotropic. Recently,
neutron diffraction demonstrated that surfboard-shaped antiferromagnetic
nanoregions coalesce above the glass transition temperature, T 55
K, and a model was proposed in which the freezing of the fluctuations of the
surfboards' magnetization leads to the anisotropic spin glass state. Given this
new model, we have carried out high resolution inelastic neutron scattering
measurements of the spin-spin correlations to understand the temperature
dependence of the intra-surfboard spin dynamics on neutron (picosecond)
time-scales. Here, we report on the temperature-dependence of the spin
fluctuations measured from single crystal FeTiO. Strong quasi-elastic
magnetic scattering, arising from intra-surfboard correlations, is observed
well above T. The spin fluctuations possess a steep energy-wave vector
relation and are indicative of strong exchange interactions, consistent with
the large Curie-Weiss temperature. As the temperature approaches T from
above, a shift in spectral weight from inelastic to elastic scattering is
observed. At various temperatures between 4 K and 300 K, a characteristic
relaxation rate of the fluctuations is determined. Despite the freezing of the
majority of the spin correlations, an inelastic contribution remains even at
base temperature, signifying the presence of fluctuating intra-surfboard spin
correlations to at least T/T 0.1 consistent with a description of
FeTiO as a hybrid between conventional and geometrically frustrated
spin glasses.Comment: 6 figure
Self-Pulsating Semiconductor Lasers: Theory and Experiment
We report detailed measurements of the pump-current dependency of the
self-pulsating frequency of semiconductor CD lasers. A distinct kink in this
dependence is found and explained using rate-equation model. The kink denotes a
transition between a region where the self-pulsations are weakly sustained
relaxation oscillations and a region where Q-switching takes place. Simulations
show that spontaneous emission noise plays a crucial role for the cross-over.Comment: Revtex, 16 pages, 7 figure
Thermoelectric Properties of Intermetallic Semiconducting RuIn3 and Metallic IrIn3
Low temperature (<400 K) thermoelectric properties of semiconducting RuIn3
and metallic IrIn3 are reported. RuIn3 is a narrow band gap semiconductor with
a large n-type Seebeck coefficient at room temperature (S(290K)~400 {\mu}V/K),
but the thermoelectric Figure of merit (ZT(290K) = 0.007) is small because of
high electrical resistivity and thermal conductivity ({\kappa}(290 K) ~ 2.0 W/m
K). IrIn3 is a metal with low thermopower at room temperature (S(290K)~20
{\mu}V/K) . Iridium substitution on the ruthenium site has a dramatic effect on
transport properties, which leads to a large improvement in the power factor
and corresponding Figure of merit (ZT(380 K) = 0.053), improving the efficiency
of the material by an over of magnitude.Comment: Submitted to JA
Recommended from our members
High-intensity drying processes: Impulse drying. Progress report on furnish evaluations for impulse drying commercialization demonstration
Laboratory and pilot scale experiments were performed to identify potential furnishes and operating parameters for upcoming high-speed pilot scale trials and commercial demonstration of impulse drying of heavy weight grades of paper. Results indicate that hydrodynamic specific surface is highly dependent on sheet formation and prehandling. Mill refined pulp and machine paper were comparable to laboratory prepared samples in regards to permeability and impulse drying. Process variables such as platen surface coating, felt type, felt moisture, and presteaming temperature profiles were investigated. Substantial improvements in sheet smoothness were achieved
Nano-magnetic droplets and implications to orbital ordering in La1-xSrxCoO3
Inelastic cold neutron scattering on LaCoO3 provided evidence for a distinct
low energy excitation at 0.6 meV coincident with the thermally induced magnetic
transition. Coexisting strong ferromagnetic (FM) and weaker antiferromagnetic
(AFM) correlations that are dynamic follow the activation to the excited state,
identified as the intermediate S=1 spin triplet. This is indicative of
dynamical orbital ordering favoring the observed magnetic interactions. With
hole doping as in La1-xSrxCoO3, the FM correlations between Co spins become
static and isotropically distributed due to the formation of FM droplets. The
correlation length and condensation temperature of these droplets increase
rapidly with metallicity due to the double exchange mechanism.Comment: To appear in Phys. Rev. Let
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