3,208 research outputs found
Statistical properties of chaotic microcavities in small and large opening cases
We study the crossover behavior of statistical properties of eigenvalues in a
chaotic microcavity with different refractive indices. The level spacing
distributions change from Wigner to Poisson distributions as the refractive
index of a microcavity decreases. We propose a non-hermitian matrix model with
random elements describing the spectral properties of the chaotic microcavity,
which exhibits the crossover behaviors as the opening strength increases.Comment: 22 pages, 6 figure
Dynamics in non-Hermitian systems with nonreciprocal coupling
We reveal that non-Hermitian Hamiltonians with nonreciprocal coupling can
achieve amplification of initial states without external gain due to a kind of
inherent source. We discuss the source and its effect on time evolution in
terms of complex eigenenergies and non-orthogonal eigenstates. Demonstrating
two extreme cases of Hamiltonians, namely one having complex eigenenergies with
orthogonal eigenstates and one having real eigenenergies with non-orthogonal
eigenstates, we elucidate the differences between the amplifications from
complex eigenenergies and from non-orthogonal eigenstates.Comment: 8 pages, 5 figure
Reconfiguration of quantum states in -symmetric quasi-one dimensional lattices
We demonstrate mesoscopic transport through quantum states in quasi-1D
lattices maintaining the combination of parity and time-reversal symmetries by
controlling energy gain and loss. We investigate the phase diagram of the
non-Hermitian system where transitions take place between unbroken and broken
-symmetric phases via exceptional points. Quantum transport in
the lattice is measured only in the unbroken phases in the energy band-but not
in the broken phases. The broken phase allows for spontaneous symmetry-broken
states where the cross-stitch lattice is separated into two identical single
lattices corresponding to conditionally degenerate eigenstates. These
degeneracies show a lift-up in the complex energy plane, caused by the
non-Hermiticity with -symmetry.Comment: 12 pages, 7 figure
Quasiattractors in coupled maps and coupled dielectric cavities
We study the origin of attracting phenomena in the ray dynamics of coupled
optical microcavities. To this end we investigate a combined map that is
composed of standard and linear map, and a selection rule that defines when
which map has to be used. We find that this system shows attracting dynamics,
leading exactly to a quasiattractor, due to collapse of phase space. For
coupled dielectric disks, we derive the corresponding mapping based on a ray
model with deterministic selection rule and study the quasiattractor obtained
from it. We also discuss a generalized Poincar\'e surface of section at
dielectric interfaces.Comment: 7 pages, 7 figure
Antiresonance induced by symmetry-broken contacts in quasi-one-dimensional lattices
We report the effect of symmetry-broken contacts on quantum transport in
quasi-one-dimensional lattices. In contrast to 1D chains, transport in
quasi-one-dimensional lattices, which are made up of a finite number of 1D
chain layers, is strongly influenced by contacts. Contact symmetry depends on
whether the contacts maintain or break the parity symmetry between the layers.
With balanced on-site potential, a flat band can be detected by asymmetric
contacts, but not by symmetric contacts. In the case of asymmetric contacts
with imbalanced on-site potential, transmission is suppressed at certain
energies. We elucidate these energies of transmission suppression related to
antiresonance using reduced lattice models and Feynman paths. These results
provide a nondestructive measurement of flat band energy which it is difficult
to detect.Comment: 8 pages, 5 figure
Quasiscarred modes and their branching behavior at an exceptional point
We study quasiscarring phenomenon and mode branching at an exceptional point
(EP) in typically deformed microcavities. It is shown that quasiscarred (QS)
modes are dominant in some mode group and their pattern can be understood by
short-time ray dynamics near the critical line. As cavity deformation
increases, high-Q and low-Q QS modes are branching in an opposite way, at an
EP, into two robust mode types showing QS and diamond patterns, respectively.
Similar branching behavior can be also found at another EP appearing at a
higher deformation. This branching behavior of QS modes has its origin on the
fact that an EP is a square-root branch point.Comment: 5 pages, 5 figure
Oscillation death in coupled counter-rotating identical nonlinear oscillators
We study oscillatory and oscillation suppressed phases in coupled
counter-rotating nonlinear oscillators. We demonstrate the existence of limit
cycle, amplitude death, and oscillation death, and also clarify the Hopf,
pitchfork, and infinite period bifurcations between them. Especially, the
oscillation death is a new type of oscillation suppressions of which the
inhomogeneous steady states are neutrally stable. We discuss the robust neutral
stability of the oscillation death in non-conservative systems via the
anti-PT-symmetric phase transitions at exceptional points in terms of
non-Hermitian systems.Comment: 7 pages, 4 figure
Flat-band localization and self-collimation of light in photonic crystals
We investigate the optical properties of a photonic crystal composed of a
quasi-one-dimensional flat-band lattice array through finite-difference
time-domain simulations. The photonic bands contain flat bands (FBs) at
specific frequencies, which correspond to compact localized states as a
consequence of destructive interference. The FBs are shown to be nondispersive
along the line, but dispersive along the
line. The FB localization of light in a single direction
only results in a self-collimation of light propagation throughout the photonic
crystal at the FB frequency.Comment: 18 single-column pages, 7 figures including graphical to
Amplitude death in a ring of nonidentical nonlinear oscillators with unidirectional coupling
We study the collective behaviors in a ring of coupled nonidentical nonlinear
oscillators with unidirectional coupling, of which natural frequencies are
distributed in a random way. We find the amplitude death phenomena in the case
of unidirectional couplings and discuss the differences between the cases of
bidirectional and unidirectional couplings. There are three main differences;
there exists neither partial amplitude death nor local clustering behavior but
oblique line structure which represents directional signal flow on the
spatio-temporal patterns in the unidirectional coupling case. The
unidirectional coupling has the advantage of easily obtaining global amplitude
death in a ring of coupled oscillators with randomly distributed natural
frequency. Finally, we explain the results using the eigenvalue analysis of
Jacobian matrix at the origin and also discuss the transition of dynamical
behavior coming from connection structure as coupling strength increases.Comment: 14 pages, 11 figure
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