24,860 research outputs found
Josephson Effects in Double-Layer Quantum Hall States
Under quite plausible assumptions on double-layer quantum Hall states with
strong interlayer correlation, we show in general framwork that coherent
tunneling of a single electron between two layers is possible. It yields
Josephson effects with unit charge tunneling. The origin is that Halperin
states in the quantum Hall states are highly degenerate in electron number
difference between two layers in the absence of electrons tunneling.Comment: 9 Pages, Revtex Inpress Int.J.Mod.Phys.
Coupled-channel study of gamma p --> K+ Lambda
A coupled-channel (CC) approach has been developed to investigate kaon
photoproduction on the nucleon. In addition to direct K+ Lambda production, our
CC approach accounts for strangeness production including K+ Lambda final state
interactions with both pi0 p and pi+ n intermediate states. Calculations for
the gamma p --> K+ Lambda reaction have been performed, and compared with the
recent data from SAPHIR, with emphasis on the CC effects. We show that the CC
effects are significant at the level of inducing 20% changes on total cross
sections; thereby, demonstrating the need to include pi N channels to correctly
describe the gamma p --> K+ Lambda reaction.Comment: 12 pages, 6 eps figures, uses elsart.cls, submitted to Phys.Lett.B;
v2: added paragraph in section
Dynamical coupled-channel model of kaon-hyperon interactions
The pi N --> KY and KY --> KY reactions are studied using a dynamical
coupled-channel model of meson-baryon interactions at energies where the baryon
resonances are strongly excited. The channels included are: pi N, K \Lambda,
and K\Sigma. The resonances considered are: N^* [S_{11}(1650), P_{11}(1710),
P_{13}(1720),D_{13}(1700)]; \Delta^* [S_{31}(1900), P_{31}(1910),
P_{33}(1920)]; \Lambda ^* [S_{01}(1670), P_{01}(1810)] \Sigma^* [P_{11}(1660),
D_{13}(1670)]; and K^*(892). The basic non-resonant \pi N --> KY and KY --> KY
transition potentials are derived from effective Lagrangians using a unitary
transformation method. The dynamical coupled-channel equations are simplified
by parametrizing the pi N -->pi N amplitudes in terms of empirical pi N
partial-wave amplitudes and a phenomenological off-shell function. Two models
have been constructed. Model A is built by fixing all coupling constants and
resonance parameters using SU(3) symmetry, the Particle Data Group values, and
results from a constituent quark model. Model B is obtained by allowing most of
the parameters to vary around the values of model A in fitting the data. Good
fits to the available data for pi^- p to K^0 \Lambda, K^0 \Sigma^0 have been
achieved. The investigated kinematics region in the center-of-mass frame goes
from threshold to 2.5 GeV. The constructed models can be imbedded into
associated dynamical coupled-channel studies of kaon photo- and
electro-production reactions.Comment: 35 pages, 11 Figure
Correlated Topological Insulators and the Fractional Magnetoelectric Effect
Topological insulators are characterized by the presence of gapless surface
modes protected by time-reversal symmetry. In three space dimensions the
magnetoelectric response is described in terms of a bulk theta term for the
electromagnetic field. Here we construct theoretical examples of such phases
that cannot be smoothly connected to any band insulator. Such correlated
topological insulators admit the possibility of fractional magnetoelectric
response described by fractional theta/pi. We show that fractional theta/pi is
only possible in a gapped time reversal invariant system of bosons or fermions
if the system also has deconfined fractional excitations and associated
degenerate ground states on topologically non-trivial spaces. We illustrate
this result with a concrete example of a time reversal symmetric topological
insulator of correlated bosons with theta = pi/4. Extensions to electronic
fractional topological insulators are briefly described.Comment: 4 pages + ref
A balancing act: Evidence for a strong subdominant d-wave pairing channel in
We present an analysis of the Raman spectra of optimally doped based on LDA band structure calculations and the
subsequent estimation of effective Raman vertices. Experimentally a narrow,
emergent mode appears in the () Raman spectra only below
, well into the superconducting state and at an energy below twice the
energy gap on the electron Fermi surface sheets. The Raman spectra can be
reproduced quantitatively with estimates for the magnitude and momentum space
structure of the s pairing gap on different Fermi surface sheets, as
well as the identification of the emergent sharp feature as a
Bardasis-Schrieffer exciton, formed as a Cooper pair bound state in a
subdominant channel. The binding energy of the exciton relative
to the gap edge shows that the coupling strength in this subdominant
channel is as strong as 60% of that in the dominant
channel. This result suggests that may be the dominant pairing
symmetry in Fe-based sperconductors which lack central hole bands.Comment: 10 pages, 6 Figure
Gravitational Corrections to Theory with Spontaneously Broken Symmetry
We consider a complex scalar theory with spontaneously broken
global U(1) symmetry, minimally coupling to perturbatively quantized Einstein
gravity which is treated as an effective theory at the energy well below the
Planck scale. Both the lowest order pure real scalar correction and the
gravitational correction to the renormalization of the Higgs sector in this
model have been investigated. Our results show that the gravitational
correction renders the renormalization of the Higgs sector in this model
inconsistent while the pure real scalar correction to it leads to a compatible
renormalization.Comment: 11 pages, 24 figure
Benchmarking a self-consistent field theory for small amphiphilic molecules
DOI: 10.1039/C2SM26352A (Paper) Soft Matter, 2012, 8, 9877-9885
This journal is © The Royal Society of Chemistry 2012A minimalist self-consistent field theory for small amphiphilic molecules is presented. The equations for
this model are less involved than those for block copolymers and are easily implemented
computationally. A new convergence technique based on a variant of Anderson mixing is also
presented which allows the equations to be solved more rapidly than block copolymer self-consistent
field theory. The computational speed up and simplicity of equations result from a lack of
configurational degrees of freedom in the amphiphilic molecular model. The omission of polymeric
flexibility leads to qualitatively different predictions compared to known diblock copolymer behaviour.University of Waterloo International Work Study Progra
Bosonic model with fractionalization
Bosonic model with unfrustrated hopping and short-range repulsive interaction
is constructed that realizes fractionalized insulator phase in two
dimensions and in zero magnetic field. Such phase is characterized as having
gapped charged excitations that carry fractional electrical charge 1/3 and also
gapped vortices above the topologically ordered ground state.Comment: 7 pages, 3 figure
Quantum Hall Ferromagnets
It is pointed out recently that the quantum Hall states in bilayer
systems behave like easy plane quantum ferromagnets. We study the
magnetotransport of these systems using their ``ferromagnetic" properties and a
novel spin-charge relation of their excitations. The general transport is a
combination of the ususal Hall transport and a time dependent transport with
time average. The latter is due to a phase slippage process in
and is characterized by two topological constants. (Figures will be
provided upon requests).Comment: 4 pages, Revtex, Ohio State Universit
Intrinsic Percolative Superconductivity in KxFe2-ySe2 Single Crystals
Magnetic field penetration and magnetization hysteresis loops (MHLs) have
been measured in KxFe2-ySe2 single crystals. The magnetic field penetration
shows a two-step feature with a very small full-magnetic-penetration field
(Hp1= 300 Oe at 2 K), and accordingly the MHL exhibits an abnormal vanishing of
the central peak near zero field below 13 K. The width of the MHL in KxFe2-ySe2
at the same temperature is in general much smaller than that measured in the
relatives Ba0.6K0.4Fe2As2 and Ba(Fe0.92Co0.08)2As2, and the MHLs in the latter
two samples show the normal central peak near zero field. All these anomalies
found in KxFe2-ySe2 can be understood in the picture that the sample is
percolative with weakly coupled superconducting islands.Comment: 5 page, 4 figure
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