42,949 research outputs found
c-Axis longitudinal magnetoresistance of the electron-doped superconductor Pr1.85Ce0.15CuO4
We report c-axis resistivity and longitudinal magnetoresistance measurements
of superconducting Pr1.85Ce0.15CuO4 single crystals. In the temperature range
13K<T<32K, a negative magnetoresistance is observed at fields just above Hc2.
Our studies suggest that this negative magnetoresistance is caused by
superconducting fluctuations. At lower temperatures (T<13K), a different
magnetoresistance behavior and a resistivity upturn are observed, whose origin
is still unknown.Comment: Accepted for publication in Phys. Rev.
Probing non-Abelian statistics of Majorana fermions in ultracold atomic superfluid
We propose an experiment to directly probe the non-Abelian statistics of
Majorana fermions by braiding them in an s-wave superfluid of ultracold atoms.
We show different orders of braiding operations give orthogonal output states
that can be distinguished through Raman spectroscopy. Realization of Majorana
bound states in an s-wave superfluid requires strong spin-orbital coupling and
a controllable Zeeman field in the perpendicular direction. We present a simple
laser configuration to generate the artificial spin-orbital coupling and the
required Zeeman field in the dark state subspace.Comment: 4 pages; Add detailed discussion of feasibility of the scheme;add
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Anisotropic Magneto-conductance of InAs Nanowire: Angle Dependent Suppression of 1D Weak Localization
The magneto-conductance of an InAs nanowire is investigated with respect to
the relative orientation between external magnetic field and the nanowire axis.
It is found that both the perpendicular and the parallel magnetic fields induce
a positive magneto-conductance. Yet the parallel magnetic field induced
longitudinal magneto-conductance has a smaller magnitude. This anisotropic
magneto-transport phenomenon is studied as a function of temperature, magnetic
field strength and at an arbitrary angle between the magnetic field and the
nanowire. We show that the observed effect is in quantitative agreement with
the suppression of one-dimensional (1D) weak localization
Criteria for accurate determination of the magnon relaxation length from the nonlocal spin Seebeck effect
The nonlocal transport of thermally generated magnons not only unveils the
underlying mechanism of the spin Seebeck effect, but also allows for the
extraction of the magnon relaxation length () in a magnetic
material, the average distance over which thermal magnons can propagate. In
this study, we experimentally explore in yttrium iron garnet (YIG)/platinum
systems much further ranges compared with previous investigations. We observe
that the nonlocal SSE signals at long distances () clearly deviate from a
typical exponential decay. Instead, they can be dominated by the nonlocal
generation of magnon accumulation as a result of the temperature gradient
present away from the heater, and decay geometrically as . We emphasize
the importance of looking only into the exponential regime (i.e., the
intermediate distance regime) to extract . With this principle, we
study as a function of temperature in two YIG films which are 2.7
and 50 m in thickness, respectively. We find to be around 15
m at room temperature and it increases to 40 m at 3.5 K. Finite
element modeling results agree with experimental studies qualitatively, showing
also a geometrical decay beyond the exponential regime. Based on both
experimental and modeling results we put forward a general guideline for
extracting from the nonlocal spin Seebeck effect.Comment: 9 pages, 7 figure
Localized form of Fock terms in nuclear covariant density functional theory
In most of the successful versions of covariant density functional theory in
nuclei, the Fock terms are not included explicitly, which leads to local
functionals and forms the basis of their widespread applicability at present.
However, it has serious consequences for the description of Gamow-Teller
resonances (GTR) and spin-dipole resonances (SDR) which can only be cured by
adding further phenomenological parameters. Relativistic Hartree-Fock models do
not suffer from these problems. They can successfully describe the GTR and SDR
as well as the isovector part of the Dirac effective mass without any
additional parameters. However, they are non-local and require considerable
numerical efforts. By the zero-range reduction and the Fierz transformation, a
new method is proposed to take into account the Fock terms in local
functionals, which retains the simplicity of conventional models and provides
proper descriptions of the spin-isospin channels and the Dirac masses.Comment: 6 pages, 4 figures, Phys. Rev. C in pres
Passively mode locked Raman laser
We report on the observation of a novel mode locked optical comb generated at
the Raman offset (Raman comb) in an optically pumped crystalline whispering
gallery mode resonator. Mode locking is confirmed via measurement of the
radio-frequency beat note produced by the optical comb on a fast photodiode.
Neither the conventional Kerr comb nor hyper-parametric oscillation is observed
when the Raman comb is present
A single intrinsic Josephson junction with double-sided fabrication technique
We make stacks of intrinsic Josephson junctions (IJJs) imbedded in the bulk
of very thin (~nm) single crystals.
By precisely controlling the etching depth during the double-sided fabrication
process, the stacks can be reproducibly tailor-made to be of any microscopic
height (), i.e. enclosing a specified number of IJJ (0-6),
including the important case of a single junction. We discuss reproducible
gap-like features in the current-voltage characteristics of the samples at high
bias.Comment: 3 pages, 4 figures, to be published in APL May. 2
Spin Polarisability of the Nucleon in the Heavy Baryon Effective Field Theory
We have constructed a heavy baryon effective field theory with photon as an
external field in accordance with the symmetry requirements similar to the
heavy quark effective field theory. By treating the heavy baryon and
anti-baryon equally on the same footing in the effective field theory, we have
calculated the spin polarisabilities of the nucleon at
third order and at fourth-order of the spin-dependent Compton scattering. At
leading order (LO), our results agree with the corresponding results of the
heavy baryon chiral perturbation theory, at the next-to-leading order(NLO) the
results show a large correction to the ones in the heavy baryon chiral
perturbation theory due to baryon-antibaryon coupling terms. The low energy
theorem is satisfied both at LO and at NLO. The contributions arising from the
heavy baryon-antibaryon vertex were found to be significant and the results of
the polarisabilities obtained from our theory is much closer to the
experimental data.Comment: 21pages, title changed, minimal correction
Local tunneling spectroscopy of the electron-doped cuprate Sm1.85Ce0.15CuO4
We present local tunneling spectroscopy in the optimally electron-doped
cuprate Sm2-xCexCuO4 x=0.15. A clear signature of the superconducting gap is
observed with an amplitude ranging from place to place and from sample to
sample (Delta~3.5-6meV). Another spectroscopic feature is simultaneously
observed at high energy above \pm 50meV. Its energy scale and temperature
evolution is found to be compatible with previous photoemission and optical
experiments. If interpreted as the signature of antiferromagnetic order in the
samples, these results could suggest the coexistence on the local scale of
antiferromagnetism and superconductivity on the electron-doped side of cuprate
superconductors
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