8,139 research outputs found
A new class of -d topological superconductor with topological classification
The classification of topological states of matter depends on spatial
dimension and symmetry class. For non-interacting topological insulators and
superconductors the topological classification is obtained systematically and
nontrivial topological insulators are classified by either integer or .
The classification of interacting topological states of matter is much more
complicated and only special cases are understood. In this paper we study a new
class of topological superconductors in dimensions which has
time-reversal symmetry and a spin conservation symmetry. We
demonstrate that the superconductors in this class is classified by
when electron interaction is considered, while the
classification is without interaction.Comment: 5 pages main text and 3 pages appendix. 1 figur
On the role of a new type of correlated disorder in extended electronic states in the Thue-Morse lattice
A new type of correlated disorder is shown to be responsible for the
appearance of extended electronic states in one-dimensional aperiodic systems
like the Thue-Morse lattice. Our analysis leads to an understanding of the
underlying reason for the extended states in this system, for which only
numerical evidence is available in the literature so far. The present work also
sheds light on the restrictive conditions under which the extended states are
supported by this lattice.Comment: 11 pages, LaTeX V2.09, 1 figure (available on request), to appear in
Physical Review Letter
Field-driven topological glass transition in a model flux line lattice
We show that the flux line lattice in a model layered HTSC becomes unstable
above a critical magnetic field with respect to a plastic deformation via
penetration of pairs of point-like disclination defects. The instability is
characterized by the competition between the elastic and the pinning energies
and is essentially assisted by softening of the lattice induced by a
dimensional crossover of the fluctuations as field increases. We confirm
through a computer simulation that this indeed may lead to a phase transition
from crystalline order at low fields to a topologically disordered phase at
higher fields. We propose that this mechanism provides a model of the low
temperature field--driven disordering transition observed in neutron
diffraction experiments on single crystals.Comment: 11 pages, 4 figures available upon request via snail mail from
[email protected]
Bragg spectroscopy of a superfluid Bose-Hubbard gas
Bragg spectroscopy is used to measure excitations of a trapped,
quantum-degenerate gas of 87Rb atoms in a 3-dimensional optical lattice. The
measurements are carried out over a range of optical lattice depths in the
superfluid phase of the Bose-Hubbard model. For fixed wavevector, the resonant
frequency of the excitation is found to decrease with increasing lattice depth.
A numerical calculation of the resonant frequencies based on Bogoliubov theory
shows a less steep rate of decrease than the measurements.Comment: 11 pages, 4 figure
An Optical-Lattice-Based Quantum Simulator For Relativistic Field Theories and Topological Insulators
We present a proposal for a versatile cold-atom-based quantum simulator of
relativistic fermionic theories and topological insulators in arbitrary
dimensions. The setup consists of a spin-independent optical lattice that traps
a collection of hyperfine states of the same alkaline atom, to which the
different degrees of freedom of the field theory to be simulated are then
mapped. We show that the combination of bi-chromatic optical lattices with
Raman transitions can allow the engineering of a spin-dependent tunneling of
the atoms between neighboring lattice sites. These assisted-hopping processes
can be employed for the quantum simulation of various interesting models,
ranging from non-interacting relativistic fermionic theories to topological
insulators. We present a toolbox for the realization of different types of
relativistic lattice fermions, which can then be exploited to synthesize the
majority of phases in the periodic table of topological insulators.Comment: 24 pages, 6 figure
Magnetization Jump in a Model for Flux Lattice Melting at Low Magnetic Fields
Using a frustrated XY model on a lattice with open boundary conditions, we
numerically study the magnetization change near a flux lattice melting
transition at low fields. In both two and three dimensions, we find that the
melting transition is followed at a higher temperature by the onset of large
dissipation associated with the zero-field XY transition. It is characterized
by the proliferation of vortex-antivortex pairs (in 2D) or vortex loops (in
3D). At the upper transition, there is a sharp increase in magnetization, in
qualitative agreement with recent local Hall probe experiments.Comment: updated figures and texts. new movies available at
http://www.physics.ohio-state.edu:80/~ryu/jj.html. Accepted for publication
in Physical Review Letter
Flux-line entanglement as the mechanism of melting transition in high-temperature superconductors in a magnetic field
The mechanism of the flux-line-lattice (FLL) melting in anisotropic high-T_c
superconductors in is clarified by Monte Carlo
simulations of the 3D frustrated XY model. The percentage of entangled flux
lines abruptly changes at the melting temperature T_m, while no sharp change
can be found in the number and size distribution of vortex loops around T_m.
Therefore, the origin of this melting transition is the entanglement of flux
lines. Scaling behaviors of physical quantities are consistent with the above
mechanism of the FLL melting. The Lindemann number is also evaluated without
any phenomenological arguments.Comment: 10 pages, 5 Postscript figures, RevTeX; changed content and figures,
Phys. Rev. B Rapid Commun. in pres
Double Resonance Nanolaser based on Coupled Slit-hole Resonator Structures
This work investigates a kind of metallic magnetic cavity based on slit-hole
resonators (SHRs). Two orthogonal hybrid magnetic resonance modes of the cavity
with a large spatial overlap are predesigned at the wavelengths of 980 nm and
1550 nm. The Yb-Er co-doped material serving as a gain medium is set in the
cavity; this enables the resonator to have high optical activity. The numerical
result shows that the strong lasing at 1550 nm may be achieved when the cavity
array is pumped at 980 nm. This double resonance nanolaser array has potential
applications in future optical devices and quantum information techniques.Comment: 11 pages, 3 figures, http://www.dsl.nju.edu/mp
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