615 research outputs found
Quantum Spin Hall Effect and Enhanced Magnetic Response by Spin-Orbit Coupling
We show that the spin Hall conductivity in insulators is related with a
magnetic susceptibility representing the strength of the spin-orbit coupling.
We use this relationship as a guiding principle to search real materials
showing quantum spin Hall effect. As a result, we theoretically predict that
bismuth will show the quantum spin Hall effect, both by calculating the helical
edge states, and by showing the non-triviality of the Z_2 topological number,
and propose possible experiments.Comment: 5 pages, 2 figures, accepted for publication in Phys. Rev. Let
Large thermoelectric figure of merit for 3D topological Anderson insulators via line dislocation engineering
We study the thermoelectric properties of three-dimensional topological
Anderson insulators with line dislocations. We show that at high densities of
dislocations the thermoelectric figure of merit ZT can be dominated by
one-dimensional topologically-protected conducting states channeled through the
lattice screw dislocations in the topological insulator materials with a
non-zero time-reversal-invariant momentum such as Bi_{1-x}Sb_x. When the
chemical potential does not exceed much the mobility edge the ZT at room
temperatures can reach large values, much higher than unity for reasonable
parameters, hence making this system a strong candidate for applications in
heat management of nano-devices.Comment: 4 pages, 3 figure
Topological nature of polarization and charge pumping in ferroelectrics
Electric polarization or transferred charge due to an adiabatic change of
external parameters is expressed in terms of a vector field defined
in the space. This vector field is characterized by strings, i.e.,
trajectories of band-crossing points. In particular, the transverse component
is given by the Biot-Savart law in a nonlocal way. For a cyclic change of
along a loop C, the linking number between this string and C
represents the amount of the pumped charge, which is quantized to be an integer
as discussed by Thouless.Comment: 5 pages including 4 figure
Dynamical Diffraction Theory for Wave Packet Propagation in Deformed Crystals
We develop a theory for the trajectory of an x ray in the presence of a
crystal deformation. A set of equations of motion for an x-ray wave packet
including the dynamical diffraction is derived, taking into account the Berry
phase as a correction to geometrical optics. The trajectory of the wave packet
has a shift of the center position due to a crystal deformation. Remarkably, in
the vicinity of the Bragg condition, the shift is enhanced by a factor (: frequency of an x ray, : gap frequency
induced by the Bragg reflection). Comparison with the conventional dynamical
diffraction theory is also made.Comment: 4 pages, 2 figures. Title change
Phase transition between the quantum spin Hall and insulator phases in 3D: emergence of a topological gapless phase
Phase transitions between the quantum spin Hall and the insulator phases in
three dimensions are studied. We find that in inversion-asymmetric systems
there appears a gapless phase between the quantum spin Hall and insulator
phases in three dimensions, which is in contrast with the two-dimensional case.
Existence of this gapless phase stems from a topological nature of gapless
points (diabolical points) in three dimensions, but not in two dimensions.Comment: 16 pages, 5 figure
Embodied responses to musical experience detected by human bio-feedback brain features in a geminoid augmented architecture
This paper presents the conceptual framework for a study of musical experience and the associated architecture centred on Human-Humanoid Interaction (HHI). On the grounds of the theoretical and experimental literature on the biological foundation of music, the grammar of music perception and the perception and feeling of emotions in music hearing, we argue that music cognition is specific and that it is realized by a cognitive capacity for music that consists of conceptual and affective constituents. We discuss the relationship between such constituents that enables understanding, that is extracting meaning from music at the different levels of the organization of sounds that are felt as bearers of affects and emotions. To account for the way such cognitive mechanisms are realized in music hearing and extended to movements and gestures we bring in the construct of tensions and of music experience as a cognitive frame. Finally, we describe the principled approach to the design and the architecture of a BCI-controlled robotic system that can be employed to map and specify the constituents of the cognitive capacity for music as well as to simulate their contribution to music meaning understanding in the context of music experience by displaying it through the Geminoid robot movements
Pfaffian and Determinant Solutions to A Discretized Toda Equation for and
We consider a class of 2 dimensional Toda equations on discrete space-time.
It has arisen as functional relations in commuting family of transfer matrices
in solvable lattice models associated with any classical simple Lie algebra
. For and , we present the solution in terms of
Pfaffians and determinants. They may be viewed as Yangian analogues of the
classical Jacobi-Trudi formula on Schur functions.Comment: Plain Tex, 9 page
Effectiveness of Structural and Nonstructural Measures on the Magnitude and Uncertainty of Future Flood Risks
Selection of tuning parameters in bridge regression models via Bayesian information criterion
We consider the bridge linear regression modeling, which can produce a sparse
or non-sparse model. A crucial point in the model building process is the
selection of adjusted parameters including a regularization parameter and a
tuning parameter in bridge regression models. The choice of the adjusted
parameters can be viewed as a model selection and evaluation problem. We
propose a model selection criterion for evaluating bridge regression models in
terms of Bayesian approach. This selection criterion enables us to select the
adjusted parameters objectively. We investigate the effectiveness of our
proposed modeling strategy through some numerical examples.Comment: 20 pages, 5 figure
Electron Correlation and Jahn-Teller Interaction in Manganese Oxides
The interplay between the electron repulsion and the Jahn-Teller
electron-phonon interation is studied with a large model for the
ferromagnetic state of the manganese oxides. These two interactions collaborate
to induce the local isospin (orbital) moments and reduce the bandwidth .
Especially the retardation effect of the Jahn-Teller phonon with the frequency
is effective to reduce , but the strong -dependence occurs
even when the Coulombic interaction is dominating () as long as
. The phonon spectrum consists of two components, i.e., the
temperature independent sharp peak at and that corresponding to the Kondo peak. These results
compared with the experiments suggest that in the metallic
manganese oxides.Comment: REVTE
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