3,737 research outputs found
Optical control of magnetization of micron-size domains in antiferromagnetic NiO single crystals
We propose Raman-induced collinear difference-frequency generation (DFG) as a
method to manipulate dynamical magnetization. When a fundamental beam
propagates along a threefold rotational axis, this coherent second-order
optical process is permitted by angular momentum conservation through the
rotational analogue of the Umklapp process. As a demonstration, we
experimentally obtained polarization properties of collinear magnetic DFG along
a [111] axis of a single crystal of antiferromagnetic NiO with micro
multidomain structure, which excellently agreed with the theoretical
prediction.Comment: 11 pages, 3 figures, submitted to Physical Review Letter
Upper Limit on Gravitational Wave Backgrounds at 0.2 Hz with Torsion-bar Antenna
We present the first upper limit on gravitational wave (GW) backgrounds at an
unexplored frequency of 0.2 Hz using a torsion-bar antenna (TOBA). A TOBA was
proposed to search for low-frequency GWs. We have developed a small-scaled TOBA
and successfully found {\Omega}gw(f) < 4.3 \times 1017 at 0.2 Hz as
demonstration of the TOBA's capabilities, where {\Omega}gw (f) is the GW energy
density per logarithmic frequency interval in units of the closure density. Our
result is the first nonintegrated limit to bridge the gap between the LIGO band
(around 100 Hz) and the Cassini band (10-6 - 10-4 Hz).Comment: 4 pages, 5 figure
The CSPP impact on non-financial firmsâ cost of borrowing and debt choice
In this study, we examine the impact of the European Central Bankâs (ECB) corporate sector purchase programme (CSPP) on euro area non-financial firmsâ cost of borrowing and choice between bank and public debt. Using a large sample of corporate bonds and syndicated loans closed between 2000 and 2019, we find that the CSPP reduced corporate bond spreads significantly, in both announcement and implementation periods. Findings also suggest that the CSPP had a positive spillover effect into the syndicated loan market during the implementation period. Our results show that there is a substitution effect between eligible bonds and equivalent loans, with non-financial firms choosing to use more corporate bonds than syndicated loan deals after the CSPP announcement, and that this effect is more important for non-switchers, those that may have more difficulty in accessing the bond market. Finally, we provide evidence that, when controlling for the CSPP, borrowers that choose corporate bonds are larger, more profitable, and have larger growth opportunity sets; and switchers with high agency costs of debt prefer bank debt.info:eu-repo/semantics/publishedVersio
High Field magnetospectroscopy to probe the 1.4eV Ni color center in diamond
A magneto-optical study of the 1.4 eV Ni color center in boron-free synthetic
diamond, grown at high pressure and high temperature, has been performed in
magnetic fields up to 56 T. The data is interpreted using the effective spin
Hamiltonian of Nazar\'e, Nevers and Davies [Phys. Rev. B 43, 14196 (1991)] for
interstitial Ni with the electronic configuration and effective
spin . Our results unequivocally demonstrate the trigonal symmetry of
the defect which preferentially aligns along the [111] growth direction on the
(111) face, but reveal the shortcomings of the crystal field model for this
particular defect.Comment: 12 pages, 13 figures, submitted to PR
Upper critical field divergence induced by mesoscopic phase separation in the organic superconductor (TMTSF)2ReO4
Due to the competition of two anion orders, (TMTSF)2ReO4, presents a phase
coexistence between semiconducting and metallic (superconducting) regions
(filaments or droplets) in a wide range of pressure. In this regime, the
superconducting upper critical field for H parallel to both c* and b' axes
present a linear part at low fields followed by a divergence above a cross-over
field. This cross-over corresponds to the 3D-2D decoupling transition expected
in filamentary or granular superconductors. The sharpness of the transition
also demonstrates that all filaments are of similar sizes and self organize in
a very ordered way. The distance between the filaments and their cross-section
are estimated.Comment: 4 pages, 4 figure
Transport through a double barrier for interacting quasi one-dimensional electrons in a Quantum Wire in the presence of a transverse magnetic field
We discuss the Luttinger Liquid behaviour of a semiconducting Quantum Wire.
We show that the measured value of the bulk critical exponent, ,
for the tunneling density of states can be easily calculated.
Then, the problem of the transport through a Quantum Dot formed by two
Quantum Point Contacts along the Quantum Wire, weakly coupled to spinless
Tomonaga-Luttinger liquids is studied, including the action of a strong
transverse magnetic field .
The known magnetic dependent peaks of the conductance, , in the
ballistic regime at a very low temperature, , have to be reflected also in
the transport at higher and in different regimes. The temperature
dependence of the maximum of the conductance peak, according to the
Correlated Sequential Tunneling theory, yields the power law , with the critical exponent, , strongly
reduced by .
This behaviour suggests the use of a similar device as a magnetic field
modulated transistor.Comment: 6 pages, 4 figure
Tight Beltrami fields with symmetry
Let be a compact orientable Seifered fibered 3-manifold without a
boundary, and an -invariant contact form on . In a suitable
adapted Riemannian metric to , we provide a bound for the volume
and the curvature, which implies the universal tightness of the
contact structure .Comment: 26 page
Strain hardening behavior of lightweight hybrid polyvinyl alcohol (PVA) fiber reinforced cement composites
Experimental results on the strain hardening and multiple cracking behaviors of polyvinyl alcohol (PVA) fiber reinforced cementitious composites under bending are reported in this paper. Different hybrid combinations of PVA fibers with different lengths and volume fractions are considered to reinforce the mortar matrix. Among different hybrid combinations, the composite containing 2% thicker PVA fibers of 12 mm length and 1% thinner PVA fibers of 6 mm length and the composite containing 2% thicker PVA fibers of 24 mm length and 1% thinner PVA fibers of 6 mm length showed the best performance in terms of highest ultimate load, largest CMOD (crack mouth opening displacement) at peak load and multiple cracking behavior. The effects of four types of light weight sands on the strain hardening and multiple cracking behavior of hybrid fiber composites are also evaluated in this study. It has been observed that the ultimate load and CMOD at peak load for all light weight hybrid fiber composites are almost the same irrespective of volume fractions of light weight sand. The composites containing finer light weight sands exhibited higher ultimate load than those containing coarser light weight sands. It is also observed that the hybrid fiber composite containing normal silica sand exhibited higher ultimate load than the composites with light weight sands
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