26,075 research outputs found
Anomalous Hall effect in the noncollinear antiferromagnet Mn5Si3
Metallic antiferromagnets with noncollinear orientation of magnetic moments
provide a playground for investigating spin-dependent transport properties by
analysis of the anomalous Hall effect. The intermetallic compound Mn5Si3 is an
intinerant antiferromagnet with collinear and noncollinear magnetic structures
due to Mn atoms on two inequivalent lattice sites. Here, magnetotransport
measurements on polycrystalline thin films and a single crystal are reported.
In all samples, an additional contribution to the anomalous Hall effect
attributed to the noncollinear arrangment of magnetic moments is observed.
Furthermore, an additional magnetic phase between the noncollinear and
collinear regimes above a metamagnetic transition is resolved in the single
crystal by the anomalous Hall effect.Comment: 7 pages, 4 figure
Bulk sediment parameters (CaCO3, TOC, >63µm) of Sites 1095, 1096, 1101 and coarse fraction analysis of Site 1095 (ODP Leg 178, Western Antarctic Peninsula)
Evidence for multiple superconducting gaps in optimally doped BaFeCoAs from infrared spectroscopy
We performed combined infrared reflection and ellipsometry measurements of
the in-plane optical reponse of single crystals of the pnictide high
temperature superconductor BaFeCoAs with = 24.5
K. We observed characteristic superconductivity-induced changes which provide
evidence for at least three different energy gaps. We show that a BCS-model of
isotropic gaps with 2 of 3.1, 4.7, and 9.2 reproduces the
experimental data rather well. We also determine the low-temperature value of
the in-plane magnetic penetration depth of 270 nm
Magnetization distribution and orbital moment in the non-Superconducting Chalcogenide Compound K0.8Fe1.6Se2
We have used polarized and unpolarized neutron diffraction to determine the
spatial distribution of the magnetization density induced by a magnetic field
of 9 T in the tetragonal phase of K0.8Fe1.6Se2. The maximum entropy
reconstruction shows clearly that most of the magnetization is confined to the
region around the iron atoms whereas there is no significant magnetization
associated with either Se or K atoms. The distribution of magnetization around
the Fe atom is slightly nonspherical with a shape which is extended along the
[0 0 1] direction in the projection. Multipolar refinement results show that
the electrons which give rise to the paramagnetic susceptibility are confined
to the Fe atoms and their distribution suggests that they occupy 3d t2g-type
orbitals with around 66% in those of xz/yz symmetry. Detail modeling of the
magnetic form factor indicates the presence of an orbital moment to the total
paramagnetic moment of Fe2+Comment: 7 pages, accepted for publication in Physical Review
Non-perturbative effects in semi-leptonic B_c decays
We discuss the impact of the soft degrees of freedom inside the B_c meson on
its rate in the semi-leptonic decay B_c -> X l nu_l where X denotes light
hadrons below the D^0 threshold. In particular we identify contributions
involving soft hadrons which are non-vanishing in the limit of massless
leptons. These contributions become relevant for a measurement of the purely
leptonic B_c decay rate, which due to helicity suppression involves a factor
m_l^2 and thus is much smaller than the contributions involving soft hadrons.Comment: LaTeX, 22 pages, 1 figur
Air hydrodynamics of the ultrafast laser-triggered spark gap
We present space and time resolved measurements of the air hydrodynamics
induced by ultrafast laser pulse excitation of the air gap between two
electrodes at high potential difference. We explore both plasma-based and
plasma-free gap excitation. The former uses the plasma left in the wake of
femtosecond filamentation, while the latter exploits air heating by
multiple-pulse resonant excitation of quantum molecular wavepackets. We find
that the cumulative electrode-driven air density depression channel initiated
by the laser plays the dominant role in the gap evolution leading to breakdown
Revealing the role of electrons and phonons in the ultrafast recovery of charge density wave correlations in 1-TiSe
Using time- and angle-resolved photoemission spectroscopy with selective
near- and mid-infrared photon excitations, we investigate the femtosecond
dynamics of the charge density wave (CDW) phase in 1-TiSe, as well as
the dynamics of CDW fluctuations at 240 K. In the CDW phase, we observe the
coherent oscillation of the CDW amplitude mode. At 240 K, we single out an
ultrafast component in the recovery of the CDW correlations, which we explain
as the manifestation of electron-hole correlations. Our momentum-resolved study
of femtosecond electron dynamics supports a mechanism for the CDW phase
resulting from the cooperation between the interband Coulomb interaction, the
mechanism of excitonic insulator phase formation, and electron-phonon coupling.Comment: 9 pages, 6 figure
Keldysh study of point-contact tunneling between superconductors
We revisit the problem of point-contact tunnel junctions involving
one-dimensional superconductors and present a simple scheme for computing the
full current-voltage characteristics within the framework of the
non-equilibrium Keldysh Green function formalism. We address the effects of
different pairing symmetries combined with magnetic fields and finite
temperatures at arbitrary bias voltages. We discuss extensively the importance
of these results for present-day experiments. In particular, we propose ways of
measuring the effects found when the two sides of the junction have dissimilar
superconducting gaps and when the symmetry of the superconducting states is not
the one of spin-singlet pairing. This last point is of relevance for the study
of the superconducting state of certain organic materials like the Bechgaard
salts and, to some extent, for ruthenium compounds.Comment: 10 pages, 4 figure
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