3,413 research outputs found
Observation of the spontaneous vortex phase in the weakly ferromagnetic superconductor ErNiBC: A penetration depth study
The coexistence of weak ferromagnetism and superconductivity in ErNiBC suggests the possibility of a spontaneous vortex phase (SVP) in which
vortices appear in the absence of an external field. We report evidence for the
long-sought SVP from the in-plane magnetic penetration depth of high-quality single crystals of ErNiBC. In addition to
expected features at the N\'{e}el temperature = 6.0 K and weak
ferromagnetic onset at K, rises to a maximum
at K before dropping sharply down to 0.1 K. We assign the
0.45 K-maximum to the proliferation and freezing of spontaneous vortices. A
model proposed by Koshelev and Vinokur explains the increasing as a consequence of increasing vortex density, and its subsequent decrease
below as defect pinning suppresses vortex hopping.Comment: 5 pages including figures; added inset to Figure 2; significant
revisions to tex
Numerical Method for Accessing the Universal Scaling Function for a Multi-Particle Discrete Time Asymmetric Exclusion Process
In the universality class of the one dimensional Kardar-Parisi-Zhang surface
growth, Derrida and Lebowitz conjectured the universality of not only the
scaling exponents, but of an entire scaling function. Since Derrida and
Lebowitz's original publication [PRL 80 209 (1998)] this universality has been
verified for a variety of continuous time, periodic boundary systems in the KPZ
universality class. Here, we present a numerical method for directly examining
the entire particle flux of the asymmetric exclusion process (ASEP), thus
providing an alternative to more difficult cumulant ratios studies. Using this
method, we find that the Derrida-Lebowitz scaling function (DLSF) properly
characterizes the large system size limit (N-->infty) of a single particle
discrete time system, even in the case of very small system sizes (N <= 22).
This fact allows us to not only verify that the DLSF properly characterizes
multiple particle discrete-time asymmetric exclusion processes, but also
provides a way to numerically solve for quantities of interest, such as the
particle hopping flux. This method can thus serve to further increase the ease
and accessibility of studies involving even more challenging dynamics, such as
the open boundary ASEP
Probing the superconducting gap symmetry of PrRuSb: A comparison with PrOsSb
We report measurements of the magnetic penetration depth in single
crystals of PrRuSb down to 0.1 K. Both and superfluid
density exhibit an exponential behavior for 0.5, with
parameters (0)/\textit{k}\textit{T} = 1.9 and
= 2900 \AA. The value of (0) is consistent with the specific-heat jump
value of = 1.87 measured elsewhere, while the value of
is consistent with the measured value of the electronic
heat-capacity coefficient . Our data are consistent with
PrRuSb being a moderate-coupling, fully-gapped superconductor. We
suggest experiments to study how the nature of the superconducting state
evolves with increasing Ru substitution for Os
Extranatural Inflation
We present a new model of inflation in which the inflaton is the extra
component of a gauge field in a 5d theory compactified on a circle. The chief
merit of this model is that the potential comes only from non-local effects so
that its flatness is not spoiled by higher dimensional operators or quantum
gravity corrections. The model predicts a red spectrum (n ~ 0.96) and a
significant production of gravitational waves (r ~ 0.11). We also comment on
the relevance of this idea to quintessence.Comment: 4 pages. Minor corrections and references added. Accepted for PR
Field-angle Dependence of the Zero-Energy Density of States in the Unconventional Heavy-Fermion Superconductor CeCoIn5
Field-angle dependent specific heat measurement has been done on the
heavy-fermion superconductor CeCoIn5 down to ~ 0.29 K, in a magnetic field
rotating in the tetragonal c-plane. A clear fourfold angular oscillation is
observed in the specific heat with the minima (maxima) occurring along the
[100] ([110]) directions. Oscillation persists down to low fields H << Hc2,
thus directly proving the existence of gap nodes. The results indicate that the
superconducting gap symmetry is most probably of dxy type.Comment: 8 pages, 3 figures, to be published in J. Phys. Condens. Matte
Doping and temperature dependence of electron spectrum and quasiparticle dispersion in doped bilayer cuprates
Within the t-t'-J model, the electron spectrum and quasiparticle dispersion
in doped bilayer cuprates in the normal state are discussed by considering the
bilayer interaction. It is shown that the bilayer interaction splits the
electron spectrum of doped bilayer cuprates into the bonding and antibonding
components around the point. The differentiation between the bonding
and antibonding components is essential, which leads to two main flat bands
around the point below the Fermi energy. In analogy to the doped
single layer cuprates, the lowest energy states in doped bilayer cuprates are
located at the point. Our results also show that the striking
behavior of the electronic structure in doped bilayer cuprates is intriguingly
related to the bilayer interaction together with strong coupling between the
electron quasiparticles and collective magnetic excitations.Comment: 9 pages, 4 figures, updated references, added figures and
discussions, accepted for publication in Phys. Rev.
Intrinsic dielectric and spectroscopic behavior of perovskite Ba(Ni1/3Nb2/3)O3–Ba(Zn1/3Nb2/3)O3 microwave dielectric ceramics
[[abstract]]Ceramics of 0.35Ba(Ni1/3Nb2/3)O3–0.65Ba(Zn1/3Nb2/3)O3 were prepared by the mixed oxide route. The effect of the cooling rate (2 °C–240 °C/h) after sintering on the microwave dielectric properties of the ceramics was examined. While the extrinsic factors, such as porosity and secondary phases, markedly influence the dielectric properties in the low-frequency regime, they have minimal effect on these properties in the high-frequency regime. The mechanisms involved in modifying the high-frequency dielectric properties of the materials were investigated by Fourier transform infrared and Raman spectroscopy, in conjunction with the Rietveld analysis of x-ray diffraction (XRD) spectra. A reduction in the cooling rate after sintering results in an increase in the high-frequency Q×f (product of dielectric Q value and measurement frequency) from 42 to 58 THz in the high-frequency regime (∼1.5 THz). Such behavior correlates very well with the increase in the B-site occupancy by Nb (deduced from the Rietveld analyses of XRD spectra) and the increase in the coherency of the lattice vibration (deduced from the reduction in the full-width-at-half-maximum of the A1g(O) Raman mode). In contrast, the cooling rate after sintering has very limited effect on the relative permittivity (varying from 40.8 to 41.9 at 1.5 THz), which is in accord with the phenomenon that the cell volume and the Raman shift of A1g(O) Raman mode are essentially independent of the cooling rate.[[booktype]]紙
Tunable magnetic interaction at the atomic scale in oxide heterostructures
We report on a systematic study of a number of structurally identical but
chemically distinct transition metal oxides in order to determine how the
material-specific properties such as the composition and the strain affect the
properties at the interface of heterostructures. Our study considers a series
of structures containing two layers of ferromagnetic SrRuO3, with
antiferromagnetic insulating manganites sandwiched in between. The results
demonstrate how to control the strength and relative orientation of interfacial
ferromagnetism in correlated electron materials by means of valence state
variation and substrate-induced strain, respectively
Acoustic Spectroscopy of the DNA in GHz range
We find a parametric resonance in the GHz range of the DNA dynamics,
generated by pumping hypersound . There are localized phonon modes caused by
the random structure of elastic modulii due to the sequence of base pairs
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