48,589 research outputs found
Berezinskii-Kosterlitz-Thouless Transition in Spin-Charge Separated Superconductor
A model for spin-charge separated superconductivity in two dimensions is
introduced where the phases of the spinon and holon order parameters couple
gauge-invariantly to a statistical gauge-field representing chiral
spin-fluctuations. The model is analyzed in the continuum limit and in the
low-temperature limit. In both cases we find that physical electronic phase
correlations show a superconducting-normal phase transition of the
Berezinskii-Kosterlitz-Thouless type, while statistical gauge-field excitations
are found to be strictly gapless. The normal-to-superconductor phase boundary
for this model is also obtained as a function of carrier density, where we find
that its shape compares favorably with that of the experimentally observed
phase diagram for the oxide superconductors.Comment: 35 pages, TeX, CSLA-P-93-
Fermion Analogy for Layered Superconducting Films in Parallel Magnetic Field
The equivalence between the Lawrence-Doniach model for films of extreme
type-II layered superconductors and a generalization of the back-scattering
model for spin-1/2 electrons in one dimension is demonstrated. This fermion
analogy is then exploited to obtain an anomalous tail for
the parallel equilibrium magnetization of the minimal double layer case in the
limit of high parallel magnetic fields for temperatures in the
critical regime.Comment: 11 pages of plain TeX, 1 postscript figur
Muon diffusion and electronic magnetism in YTiO
We report a SR study in a YTiO single crystal. We observe
slow local field fluctuations at low temperature which become faster as the
temperature is increased. Our analysis suggests that muon diffusion is present
in this system and becomes small below 40 K and therefore incoherent. A
surprisingly strong electronic magnetic signal is observed with features
typical for muons thermally diffusing towards magnetic traps below K and released from them above this temperature. We attribute the traps to
Ti defects in the diluted limit. Our observations are highly relevant to
the persistent spin dynamics debate on TiO pyrochlores and their
crystal quality
The Higgs decay rate to two photons in a model with two fermiophobic-Higgs doublets
We consider a three Higgs doublet model with an symmetry in which
beside the SM-like doublet there are two fermiophobic doublets. Due to the new
charged scalars there is an enhancement in the two-photon decay while the other
channels have the same decay widths that the SM neutral Higgs. The fermiophobic
scalars are mass degenerated unless soft terms breaking the symmetry are
added.Comment: typos were corrected, the figures have been modified and the
conclusions were increased. Still contains 15 pages, 2 figure
Moving embedded lattice solitons
It was recently proved that isolated unstable "embedded lattice solitons"
(ELS) may exist in discrete systems. The discovery of these ELS gives rise to
relevant questions such as the following: are there continuous families of
ELS?, can ELS be stable?, is it possible for ELS to move along the lattice?,
how do ELS interact?. The present work addresses these questions by showing
that a novel differential-difference equation (a discrete version of a complex
mKdV equation) has a two-parameter continuous family of exact ELS. The
numerical tests reveal that these solitons are stable and robust enough to
withstand collisions. The model may apply to the description of a Bose-Einstein
condensate with dipole-dipole interactions between the atoms, trapped in a deep
optical-lattice potential.Comment: 13 pages, 11 figure
Thermal properties of gauge-fields common to anyon superconductors and spin-liquids
The thermally driven confinement-deconfinement transition exhibited by
lattice quantum electrodynamics in two space dimensions is re-examined in the
context of the statistical gauge-fields common to anyon superconductors and to
spin-liquids. Particle-hole excitations in both systems are bound by a
confining string at temperatures below the transition temperature . We
argue that coincides with the actual critical temperature for anyon
superconductivity. The corresponding specific-heat contribution, however, shows
a {\it smooth} peak just below characteristic of certain high-temperature
superconductors.Comment: 13 pgs, TeX, to appear in Physical Review B (minor revisions
Electromechanical Imaging of Biological Systems with Sub-10 nm Resolution
Electromechanical imaging of tooth dentin and enamel has been performed with
sub-10 nm resolution using piezoresponse force microscopy. Characteristic
piezoelectric domain size and local protein fiber ordering in dentin have been
determined. The shape of a single collagen fibril in enamel is visualized in
real space and local hysteresis loops are measured. Because of the ubiquitous
presence of piezoelectricity in biological systems, this approach is expected
to find broad application in high-resolution studies of a wide range of
biomaterials.Comment: 12 pages, 4 figures, submitted for publication in Appl. Phys. Let
Nesting Induced Peierls-type Instability for Compressed Li-CI16
Alkalies are considered to be simple metals at ambient conditions. However,
recently reported theoretical and experimental results have shown an unexpected
and intriguing correlation between complex structures and an enhanced
superconducting transition temperature in lithium under pressure. In this
article we analyze the pressure induced Fermi surface deformation in bcc
lithium, and its relation to the observed cI16 structure. According to our
calculations, the Fermi surface becomes increasingly anisotropic with pressure
and develops an extended nesting along the bcc [121] direction. This nesting
induces a phonon instability of both transverse modes at N, so that a
Peierls-type mechanism is proposed to explain the stability of Li-cI16.Comment: Proceedings of Fukuoka 2006 Conference on Novel Pressure-induced
Phenomena in Condensed Matter Systems. To be published in J. Phys. Soc. Jpn.
2 pages and 3 figure
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