49,920 research outputs found
Phase transitions in the Shastry-Sutherland lattice
Two recently developed theoretical approaches are applied to the
Shastry-Sutherland lattice, varying the ratio between the couplings on
the square lattice and on the oblique bonds. A self-consistent perturbation,
starting from either Ising or plaquette bond singlets, supports the existence
of an intermediate phase between the dimer phase and the Ising phase. This
existence is confirmed by the results of a renormalized excitonic method. This
method, which satisfactorily reproduces the singlet triplet gap in the dimer
phase, confirms the existence of a gapped phase in the interval
Comment: Submited for publication in Phys. Rev.
Phase Ordering Dynamics of Theory with Hamiltonian Equations of Motion
Phase ordering dynamics of the (2+1)- and (3+1)-dimensional theory
with Hamiltonian equations of motion is investigated numerically. Dynamic
scaling is confirmed. The dynamic exponent is different from that of the
Ising model with dynamics of model A, while the exponent is the same.Comment: to appear in Int. J. Mod. Phys.
Short-time critical dynamics of the three-dimensional systems with long-range correlated disorder
Monte Carlo simulations of the short-time dynamic behavior are reported for
three-dimensional Ising and XY models with long-range correlated disorder at
criticality, in the case corresponding to linear defects. The static and
dynamic critical exponents are determined for systems starting separately from
ordered and disordered initial states. The obtained values of the exponents are
in a good agreement with results of the field-theoretic description of the
critical behavior of these models in the two-loop approximation and with our
results of Monte Carlo simulations of three-dimensional Ising model in
equilibrium state.Comment: 24 RevTeX pages, 12 figure
Trapping and guiding surface plasmons in curved graphene landscapes
We demonstrate that graphene placed on top of structured substrates offers a
novel approach for trapping and guiding surface plasmons. A monolayer graphene
with a spatially varying curvature exhibits an effective trapping potential for
graphene plasmons near curved areas such as bumps, humps and wells. We derive
the governing equation for describing such localized channel plasmons guided by
curved graphene and validate our theory by the first-principle numerical
simulations. The proposed confinement mechanism enables plasmon guiding by the
regions of maximal curvature, and it offers a versatile platform for
manipulating light in planar landscapes. In addition, isolated deformations of
graphene such as bumps are shown to support localized surface modes and
resonances suggesting a new way to engineer plasmonic metasurfaces.Comment: 6 pages, 4 figure
Persistence in the Zero-Temperature Dynamics of the Diluted Ising Ferromagnet in Two Dimensions
The non-equilibrium dynamics of the strongly diluted random-bond Ising model
in two-dimensions (2d) is investigated numerically.
The persistence probability, P(t), of spins which do not flip by time t is
found to decay to a non-zero, dilution-dependent, value . We find
that decays exponentially to zero at large times.
Furthermore, the fraction of spins which never flip is a monotonically
increasing function over the range of bond-dilution considered. Our findings,
which are consistent with a recent result of Newman and Stein, suggest that
persistence in disordered and pure systems falls into different classes.
Furthermore, its behaviour would also appear to depend crucially on the
strength of the dilution present.Comment: some minor changes to the text, one additional referenc
Fast geometric gate operation of superconducting charge qubits in circuit QED
A scheme for coupling superconducting charge qubits via a one-dimensional
superconducting transmission line resonator is proposed. The qubits are working
at their optimal points, where they are immune to the charge noise and possess
long decoherence time. Analysis on the dynamical time evolution of the
interaction is presented, which is shown to be insensitive to the initial state
of the resonator field. This scheme enables fast gate operation and is readily
scalable to multiqubit scenario
- …