10,096 research outputs found
Intra-Landau level polarization effect for a striped Hall gas
We calculate the polarization function including only intra-Landau level
correlation effects of striped Hall gas. Using the polarization function, the
dielectric function, the dispersion of the plasmon and the correlation energy
are computed in a random phase approximation (RPA) and generalized random phase
approximation (GRPA). The plasmon becomes anisotropic and gapless owing to the
anisotropy of the striped Hall gas and two dimensionality of the quantum Hall
system. The plasmon approximately agrees with the phonon derived before by the
single mode approximation. The (G)RPA correlation energy is compared with other
numerical calculations.Comment: 15 pages,15 figures, revtex4, published versio
Integer Quantum Hall Effect with Realistic Boundary Condition : Exact Quantization and Breakdown
A theory of integer quantum Hall effect(QHE) in realistic systems based on
von Neumann lattice is presented. We show that the momentum representation is
quite useful and that the quantum Hall regime(QHR), which is defined by the
propagator in the momentum representation, is realized. In QHR, the Hall
conductance is given by a topological invariant of the momentum space and is
quantized exactly. The edge states do not modify the value and topological
property of in QHR. We next compute distribution of current based
on effective action and find a finite amount of current in the bulk and the
edge, generally. Due to the Hall electric field in the bulk, breakdown of the
QHE occurs. The critical electric field of the breakdown is proportional to
and the proportional constant has no dependence on Landau levels in
our theory, in agreement with the recent experiments.Comment: 48 pages, figures not included, some additions and revision
Compressible Anisotropic States around the Half-Filled Landau Levels
Using the von Neumann lattice formalism, we study compressible anisotropic
states around the half-filled Landau levels in the quantum Hall system. In
these states the unidirectional charge density wave (UCDW) state seems to be
the most plausible state. The charge density profile and Hartree-Fock energy of
the UCDW are calculated self-consistently. The wave length dependence of the
energy for the UCDW is also obtained numerically. We show that the UCDW is
regarded as a collection of the one-dimensional lattice Fermi-gas systems which
extend to the uniform direction. The kinetic energy of the gas system is
generated dynamically from the Coulomb interaction.Comment: 6 pages, 5 figures, accepted version for publication in PR
Axial Anomaly Effect in Chiral p-wave Superconductor
We analyze the chiral p-wave superconductor in the low temperature region.
The superconductor has a epsilon_{x} p_{x} + i epsilon_{y} p_{y}-wave gap in
two dimensional space (2D). Near the second superconducting transition point,
the system could be described by a quasi-1D chiral p-wave model in 2D. The
axial anomaly occurs in such a model and causes an accumulation of the
quasiparticle in an inhomogeneous magnetic field. The effect is related to the
winding number of the gap.Comment: 12 pages, 1 figure, RevTex. The final version is accepted for
publication in J. Phys. Soc. Jp
Superconductivity under pressure in the Dirac semimetal PdTe2
The Dirac semimetal PdTe was recently reported to be a type-I
superconductor (1.64 K, mT) with unusual
superconductivity of the surface sheath. We here report a high-pressure study,
GPa, of the superconducting phase diagram extracted from
ac-susceptibility and transport measurements on single crystalline samples.
shows a pronounced non-monotonous variation with a maximum 1.91 K around 0.91 GPa, followed by a gradual decrease to 1.27 K at 2.5 GPa.
The critical field of bulk superconductivity in the limit ,
, follows a similar trend and consequently the -curves
under pressure collapse on a single curve: .
Surface superconductivity is robust under pressure as demonstrated by the large
superconducting screening signal that persists for applied dc-fields . Surprisingly, for GPa the superconducting transition
temperature at the surface is larger than of the bulk. Therefore
surface superconductivity may possibly have a non-trivial nature and is
connected to the topological surface states detected by ARPES. We compare the
measured pressure variation of with recent results from band structure
calculations and discuss the importance of a Van Hove singularity.Comment: manuscript 9 pages with 8 figures + supplemental material 3 pages
with 6 figure
The square-lattice spiral magnet Ba_2CuGe_2O_7 in an in-plane magnetic field
The magnetic structure of Ba_2CuGe_2O_7 is investigated by neutron
diffraction in magnetic fields applied along several directions in the
plane of the crystal. In relatively weak fields, ~T, the
propagation vector of the spin-spiral rotates to form a finite angle with the
field direction. This angle depends on the orientation of itself. The
rotation of the propagation vector is accompanied by a re-orientation of the
plane of spin rotation in the spiral. The observed behaviour is well described
by a continuous-limit form of a free energy functional that includes exchange
and Dzyaloshinskii-Moriya interactions, as well as the Zeeman energy and an
empirical anisotropy term.Comment: 7 pages, 6 figure
Persistence of Covalent Bonding in Liquid Silicon Probed by Inelastic X-ray Scattering
Metallic liquid silicon at 1787K is investigated using x-ray Compton
scattering. An excellent agreement is found between the measurements and the
corresponding Car-Parrinello molecular dynamics simulations. Our results show
persistence of covalent bonding in liquid silicon and provide support for the
occurrence of theoretically predicted liquid-liquid phase transition in
supercooled liquid states. The population of covalent bond pairs in liquid
silicon is estimated to be 17% via a maximally-localized Wannier function
analysis. Compton scattering is shown to be a sensitive probe of bonding
effects in the liquid state.Comment: 5pages, 3 postscript figure
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