1,005 research outputs found
Transmission resonance in a composite plasmonic structure
The design, fabrication, and optical properties of a composite plasmonic
structure, a two-dimentional array of split-ring resonators inserted into
periodic square holes of a metal film, have been reported. A new type of
transmission resonance, which makes a significant difference from the
conventional peaks, has been suggested both theoretically and experimentally.
To understand this effect, a mechanism of ring- resonance induced dipole
emission is proposed.Comment: 14 pages, 4 figure
Onset of chaotic gravitational lensing in non-Kerr rotating black holes with quadrupole mass moment
In the electromagnetic channel, chaotic gravitational lensing is a peculiar
phenomenon in strong gravitational lensing. In this work, we analyze the
properties and emergence of chaotic gravitational lensing in the Manko-Novikov
black hole spacetime. Aiming to understand better the underlying physics, we
elaborate on the boundaries of the accessible region in terms of the analyses
of the contours of the effective potentials. The latter is associated with the
two roots of a quadratic equation. In particular, we explore its interplay with
ergoregion, which leads to specific features of the effective potentials, such
as the emergence of cuspy edge and the formation of {\it pocket}, that serves
as a static constraint on the geodesics. Besides, we investigate the properties
of the radial and angular accelerations at the turning points in photons'
trajectories. Moreover, the accelerations are analyzed, which is argued to
provide a kinematic constraint on the geodesics. It is concluded that the onset
of the chaotic lensing is crucially related to both constraints, and as a
result, an arbitrarily slight deviation in the incident photon is significantly
amplified during the course of evolution through an extensive period,
demonstrating the complexity in the highly nonlinear deterministic
gravitational system.Comment: 18 pages, 13 figure
Enhanced superconductivity and various edge modes in modulated - chains
We numerically investigate the ground state of the extended -
Hamiltonian with periodic local modulations in one dimension by using the
density-matrix renormalization group method. Examining charge and spin
excitation gaps, as well as the pair binding energy, with extrapolated results
to the thermodynamic limit, we obtain a rich ground-state phase diagram
consisting of the metallic state, the superconducting state, the phase
separation, and insulating states at commensurate fillings. Compared to the
homogeneous 1D - model, the superconductivity is greatly enhanced and
stabilized by the flat-band structure. This superconducting state in
quasi-periodic chains shares similar properties with ladder systems:
significant negative pair binding energy occurs, and the singlet pairing
correlation function dominates with the algebraic decay while the
single-particle Green's function and spin correlation function decay
exponentially. On the other hand, quasi-periodicity leads to nontrivial
topological nature in insulating states, characterized by different integer
Chern numbers at different fillings. Due to the interplay among the topology,
the interaction, and the 1D confinement, gapless edge modes show strong
spin-charge separation and in different regions can relate to different
collective modes, which are the charge of a single fermion, the magnon, and the
singlet-pair. We also find two interaction driven topological transitions: i)
at particle filling , the low-energy edge excitations change from the
magnon to singlet-pair, accompanied with pair formation in bulk; and ii) at
, while the gapless edge mode remains the charge of a single fermion,
there is a gap-closing point and a -phase shift in the quasi-particle
spectrum.Comment: 10 pages,15 figure
Large-gap quantum spin Hall insulators in tin films
The search of large-gap quantum spin Hall (QSH) insulators and effective
approaches to tune QSH states is important for both fundamental and practical
interests. Based on first-principles calculations we find two-dimensional tin
films are QSH insulators with sizable bulk gaps of 0.3 eV, sufficiently large
for practical applications at room temperature. These QSH states can be
effectively tuned by chemical functionalization and by external strain. The
mechanism for the QSH effect in this system is band inversion at the \Gamma
point, similar to the case of HgTe quantum well. With surface doping of
magnetic elements, the quantum anomalous Hall effect could also be realized
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