37,338 research outputs found
Laser induced THz emission from femtosecond photocurrents in Co/ZnO/Pt and Co/Cu/Pt multilayers
The ultrashort laser excitation of Co/Pt magnetic heterostructures can
effectively generate spin and charge currents at the interfaces between
magnetic and nonmagnetic layers. The direction of these photocurrents can be
controlled by the helicity of the circularly polarized laser light and an
external magnetic field. Here, we employ THz time-domain spectroscopy to
investigate further the role of interfaces in these photo-galvanic phenomena.
In particular, the effects of either Cu or ZnO interlayers on the photocurrents
in Co/X/Pt (X = Cu, ZnO) have been studied by varying the thickness of the
interlayers up to 5 nm. The results are discussed in terms of spin-diffusion
phenomena and interfacial spin-orbit torque.Comment: 15 pages, 6 figures, 2 table
Using zeros of the canonical partition function map to detect signatures of a Berezinskii-Kosterlitz-Thouless transition
Using the two dimensional model as a test case, we show that
analysis of the Fisher zeros of the canonical partition function can provide
signatures of a transition in the Berezinskii-Kosterlitz-Thouless ()
universality class. Studying the internal border of zeros in the complex
temperature plane, we found a scenario in complete agreement with theoretical
expectations which allow one to uniquely classify a phase transition as in the
class of universality. We obtain in excellent accordance with
previous results. A careful analysis of the behavior of the zeros for both
regions and in the
thermodynamic limit show that goes to zero in the former
case and is finite in the last one
Phase diagram of the antiferromagnetic XY model in two dimensions in a magnetic field
The phase diagram of the quasi-two-dimensional easy-plane antiferromagnetic
model, with a magnetic field applied in the easy plane, is studied using the
self-consistent harmonic approximation. We found a linear dependence of the
transition temperature as a function of the field for large values of the
field. Our results are in agreement with experimental data for the spin-1
honeycomb compound BaNi_2V_2O_3Comment: 3 page
Proton decay matrix elements with domain-wall fermions
Hadronic matrix elements of operators relevant to nucleon decay in grand
unified theories are calculated numerically using lattice QCD. In this context,
the domain-wall fermion formulation, combined with non-perturbative
renormalization, is used for the first time. These techniques bring reduction
of a large fraction of the systematic error from the finite lattice spacing.
Our main effort is devoted to a calculation performed in the quenched
approximation, where the direct calculation of the nucleon to pseudoscalar
matrix elements, as well as the indirect estimate of them from the nucleon to
vacuum matrix elements, are performed. First results, using two flavors of
dynamical domain-wall quarks for the nucleon to vacuum matrix elements are also
presented to address the systematic error of quenching, which appears to be
small compared to the other errors. Our results suggest that the representative
value for the low energy constants from the nucleon to vacuum matrix elements
are given as |alpha| simeq |beta| simeq 0.01 GeV^3. For a more reliable
estimate of the physical low energy matrix elements, it is better to use the
relevant form factors calculated in the direct method. The direct method tends
to give smaller value of the form factors, compared to the indirect one, thus
enhancing the proton life-time; indeed for the pi^0 final state the difference
between the two methods is quite appreciable.Comment: 56 pages, 17 figures, a comment and two references added in the
introduction, typo corrected in Eq.1
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