1,751 research outputs found
Superconductor-Nanowire Devices from Tunneling to the Multichannel Regime: Zero-Bias Oscillations and Magnetoconductance Crossover
We present transport measurements in superconductor-nanowire devices with a
gated constriction forming a quantum point contact. Zero-bias features in
tunneling spectroscopy appear at finite magnetic fields, and oscillate in
amplitude and split away from zero bias as a function of magnetic field and
gate voltage. A crossover in magnetoconductance is observed: Magnetic fields
above ~ 0.5 T enhance conductance in the low-conductance (tunneling) regime but
suppress conductance in the high-conductance (multichannel) regime. We consider
these results in the context of Majorana zero modes as well as alternatives,
including Kondo effect and analogs of 0.7 structure in a disordered nanowire.Comment: Supplemental Material here:
https://dl.dropbox.com/u/1742676/Churchill_Supplemental.pd
Conformal linear gravity in de Sitter space
It has been shown that the theory of linear conformal quantum gravity must
include a tensor field of rank-3 and mixed symmetry [1]. In this paper, we
obtain the corresponding field equation in de Sitter space. Then, in order to
relate this field with the symmetric tensor field of rank-2, \K_{\alpha\beta}
related to graviton, we will define homomorphisms between them. Our main result
is that if one insists \K_{\alpha\beta} to be a unitary irreducible
representation of de Sitter and conformal groups it must satisfy a filed
equation of order 6, which is obtained.Comment: 10 page
Atomic Structure and Magnetism of Ordered and Disordered Alâ.â Feâ.â ââMnâ Alloys
The equiatomic FeAl alloy has been modified by partial substitution of Mn for Fe, and its magnetic and structural properties investigated by neutron diffraction (ND), x-ray absorption fine structure (XAFS) spectroscopy, Mössbauer spectroscopy (MS), and SQUID magnetometry both for the ordered (B2) and disordered states. The unit cell volume is measured to increase linearly with Mn concentration. XAFS measurements indicate local structural displacements occur at the Mn sites in both ordered and disordered states that may act to frustrate long-range magnetic order (LRMO). Although MS and ND show no evidence of LRMO, SQUID magnetometry indicates an induced movement in the ordered state that increases with disorder but does not saturate at fields up to 5 T
Experimental determination of the evolution of the Bjorken integral at low Q^2
We extract the Bjorken integral Gamma^{p-n}_1 in the range 0.17 < Q^2 < 1.10
GeV^2 from inclusive scattering of polarized electrons by polarized protons,
deuterons and 3He, for the region in which the integral is dominated by nucleon
resonances. These data bridge the domains of the hadronic and partonic
descriptions of the nucleon. In combination with earlier measurements at higher
Q^2, we extract the non-singlet twist-4 matrix element f_2.Comment: Quoted world data updated. Minor change in some results, Minor
rephrasin
Measurement of double beta decay of Âčâ°â°Mo to excited states in the NEMO 3 experiment
The double beta decay of Âčâ°â°Mo to the 0_{1}^{+} and 2_{1}^{+} excited states of Âčâ°â°Ru is studied using the NEMO 3 data. After the analysis of 8024 h of data the half-life for the two-neutrino double beta decay of Âčâ°â°Mo to the excited 0_{1}^{+} state is measured to be T_{1/2}^{2v} = [5.7_{-0.9}^{+1.3} (stat.) ± 0.8 (syst.)] x 10ÂČâ° y. The signal-to-background ratio is equal to 3. Information about energy and angular distributions of emitted electrons is also obtained. No evidence for neutrinoless double beta decay to the excited 0_{1}^{+} state has been found. The corresponding half-life limit is T_{1/2}^{0v} (0âșâ0_{1}^{+}) > 8.9 x 10ÂČÂČ y (at 90% C.L.). The search for the double beta decay to the 2_{1}^{+} excited state has allowed the determination of limits on the half-life for the two neutrino mode T_{1/2}^{0v} (0âșâ2_{1}^{+}) > 1.1 x 10ÂČÂč y (at 90% C.L.) and for the neutrinoless mode T_{1/2}^{0v} (0âșâ2_{1}^{+}) > 1.6 x 10ÂČÂł y (at 90% C.L.)
Matter-Wave Solitons in an F=1 Spinor Bose-Einstein Condensate
Following our previous work [J. Ieda, T. Miyakawa, M. Wadati,
cond-mat/0404569] on a novel integrable model describing soliton dynamics of an
F=1 spinor Bose--Einstein condensate, we discuss in detail the properties of
the multi-component system with spin-exchange interactions. The exact multiple
bright soliton solutions are obtained for the system where the mean-field
interaction is attractive (c_0 < 0) and the spin-exchange interaction is
ferromagnetic (c_2 < 0). A complete classification of the one-soliton solution
with respect to the spin states and an explicit formula of the two-soliton
solution are presented. For solitons in polar state, there exists a variety of
different shaped solutions including twin peaks. We show that a "singlet pair"
density can be used to distinguish those energetically degenerate solitons. We
also analyze collisional effects between solitons in the same or different spin
state(s) by computing the asymptotic forms of their initial and final states.
The result reveals that it is possible to manipulate the spin dynamics by
controlling the parameters of colliding solitons.Comment: 12 pages, 9 figures, to appear in J. Phys. Soc. Jpn. Vol.73 No.11
(2004
Higher moments of nucleon spin structure functions in heavy baryon chiral perturbation theory and in a resonance model
The third moment of the twist-3 part of the nucleon spin structure
function is generalized to arbitrary momentum transfer and is
evaluated in heavy baryon chiral perturbation theory (HBChPT) up to order
and in a unitary isobar model (MAID). We show how to link
as well as higher moments of the nucleon spin structure functions
and to nucleon spin polarizabilities. We compare our results with the
most recent experimental data, and find a good description of these available
data within the unitary isobar model. We proceed to extract the twist-4 matrix
element which appears in the suppressed term in the twist
expansion of the spin structure function for proton and neutron.Comment: 30 pages, 7 figure
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