36,324 research outputs found
High-pressure study of the basal-plane anisotropy of the upper critical field of the topological superconductor SrxBi2Se3
We report a high-pressure transport study of the upper-critical field,
, of the topological superconductor SrBiSe ( K). was measured for magnetic fields directed along two
orthogonal directions, and , in the trigonal basal plane. While
superconductivity is rapidly suppressed at the critical pressure
GPa, the pronounced two-fold basal-plane anisotropy at K, recently reported at ambient pressure (Pan et al., 2016), is
reinforced and attains a value of at the highest pressure (2.2 GPa).
The data reveal that the unconventional superconducting state with broken
rotational symmetry is robust under pressure
Specific heat and thermal conductivity of ferromagnetic magnons in Yttrium Iron Garnet
The specific heat and thermal conductivity of the insulating ferrimagnet
YFeO (Yttrium Iron Garnet, YIG) single crystal were measured
down to 50 mK. The ferromagnetic magnon specific heat shows a
characteristic dependence down to 0.77 K. Below 0.77 K, a downward
deviation is observed, which is attributed to the magnetic dipole-dipole
interaction with typical magnitude of 10 eV. The ferromagnetic magnon
thermal conductivity does not show the characteristic
dependence below 0.8 K. To fit the data, both magnetic defect
scattering effect and dipole-dipole interaction are taken into account. These
results complete our understanding of the thermodynamic and thermal transport
properties of the low-lying ferromagnetic magnons.Comment: 5 pages, 5 figure
Suppression of low-energy Andreev states by a supercurrent in YBa_2Cu_3O_7-delta
We report a coherence-length scale phenomenon related to how the high-Tc
order parameter (OP) evolves under a directly-applied supercurrent. Scanning
tunneling spectroscopy was performed on current-carrying YBa_2Cu_3O_7-delta
thin-film strips at 4.2K. At current levels well below the theoretical
depairing limit, the low-energy Andreev states are suppressed by the
supercurrent, while the gap-like structures remain unchanged. We rule out the
likelihood of various extrinsic effects, and propose instead a model based on
phase fluctuations in the d-wave BTK formalism to explain the suppression. Our
results suggest that a supercurrent could weaken the local phase coherence
while preserving the pairing amplitude. Other possible scenarios which may
cause the observed phenomenon are also discussed.Comment: 6 pages, 4 figures, to appear in Physical Review
Photoemission Spectroscopy of Magnetic and Non-magnetic Impurities on the Surface of the BiSe Topological Insulator
Dirac-like surface states on surfaces of topological insulators have a chiral
spin structure that suppresses back-scattering and protects the coherence of
these states in the presence of non-magnetic scatterers. In contrast, magnetic
scatterers should open the back- scattering channel via the spin-flip processes
and degrade the state's coherence. We present angle-resolved photoemission
spectroscopy studies of the electronic structure and the scattering rates upon
adsorption of various magnetic and non-magnetic impurities on the surface of
BiSe, a model topological insulator. We reveal a remarkable
insensitivity of the topological surface state to both non-magnetic and
magnetic impurities in the low impurity concentration regime. Scattering
channels open up with the emergence of hexagonal warping in the high-doping
regime, irrespective of the impurity's magnetic moment.Comment: 5 pages, 4 figure
Superconductivity and magnetic order in the non-centrosymmetric Half Heusler compound ErPdBi
We report superconductivity at K and magnetic order at K in the semi-metallic noncentrosymmetric Half Heusler compound ErPdBi.
The upper critical field, , has an unusual quasi-linear temperature
variation and reaches a value of 1.6 T for . Magnetic order is
found below and is suppressed at T for . Since , the interaction of superconductivity and magnetism
is expected to give rise to a complex ground state. Moreover, electronic
structure calculations show ErPdBi has a topologically nontrivial band
inversion and thus may serve as a new platform to study the interplay of
topological states, superconductivity and magnetic order.Comment: 6 pages, 5 figures; accepted for publication in Europhysics Letter
Multilevel semantic analysis and problem-solving in the flight domain
A computer based cockpit system which is capable of assisting the pilot in such important tasks as monitoring, diagnosis, and trend analysis was developed. The system is properly organized and is endowed with a knowledge base so that it enhances the pilot's control over the aircraft while simultaneously reducing his workload
Measurement of an Exceptionally Weak Electron-Phonon Coupling on the Surface of the Topological Insulator BiSe Using Angle-Resolved Photoemission Spectroscopy
Gapless surface states on topological insulators are protected from elastic
scattering on non-magnetic impurities which makes them promising candidates for
low-power electronic applications. However, for wide-spread applications, these
states should have to remain coherent at ambient temperatures. Here, we studied
temperature dependence of the electronic structure and the scattering rates on
the surface of a model topological insulator, BiSe, by high resolution
angle-resolved photoemission spectroscopy. We found an extremely weak
broadening of the topological surface state with temperature and no anomalies
in the state's dispersion, indicating exceptionally weak electron-phonon
coupling. Our results demonstrate that the topological surface state is
protected not only from elastic scattering on impurities, but also from
scattering on low-energy phonons, suggesting that topological insulators could
serve as a basis for room temperature electronic devices.Comment: published version, 5 pages, 4 figure
Demonstration of Non-Deterministic Quantum Logic Operations using Linear Optical Elements
Knill, Laflamme, and Milburn recently showed that non-deterministic quantum
logic operations could be performed using linear optical elements, additional
photons (ancilla), and post-selection based on the output of single-photon
detectors [Nature 409, 46 (2001)]. Here we report the experimental
demonstration of two logic devices of this kind, a destructive controlled-NOT
(CNOT) gate and a quantum parity check. These two devices can be combined with
a pair of entangled photons to implement a conventional (non-destructive) CNOT
that succeeds with a probability of 1/4.Comment: 4 pages, 5 figures; Minor change
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