1,670 research outputs found
Two-dimensional melting far from equilibrium in a granular monolayer
We report an experimental investigation of the transition from a hexagonally
ordered solid phase to a disordered liquid in a monolayer of vibrated spheres.
The transition occurs as the intensity of the vibration amplitude is increased.
Measurements of the density of dislocations and the positional and
orientational correlation functions show evidence for a dislocation-mediated
continuous transition from a solid phase with long-range order to a liquid with
only short-range order. The results show a strong similarity to simulations of
melting of hard disks in equilibrium, despite the fact that the granular
monolayer is far from equilibrium due to the effects of interparticle
dissipation and the vibrational forcing.Comment: 4 pages, 4 figure
Retrieving the Size of Deep-subwavelength Objects via Tunable Optical Spin-Orbit Coupling
We propose a scheme to retrieve the size parameters of a nano-particle on a
glass substrate at a scale much smaller than the wavelength. This is achieved
by illuminating the particle using two plane waves to create rich and
non-trivial local polarization distributions, and observing the far-field
scattering pattern into the substrate. A simple dipole model which exploits
tunneling effect of evanescent field into regions beyond the critical angle, as
well as directional scattering due to spin-orbit coupling is developed, to
relate the particle's shape, size and position to the far-field scattering with
remarkable sensitivity. Our method brings about a far-field super-resolution
imaging scheme based on the interaction of vectorial light with nanoparticles
Non-negligible magnetic dipole scattering from metallic nanowire for ultrasensitive deflection sensing
It is generally believed that when a single metallic nanowire is sufficiently
small, it scatters like a point electric dipole. We show theoretically when a
metallic nanowire is placed inside specially designed beams, the non-negligible
magnetic dipole contribution along with the electric dipole resonance can lead
to unidirectional scattering in the far-field, fulfilling Kerker's condition.
Remarkably, this far-field unidirectional scattering encodes information that
is highly dependent on the nanowire's deflection at a scale much smaller than
the wavelength. The special role of small but non-negligible magnetic response
and plasmonic resonance are highlighted for this extreme sensitivity as
compared with the dielectric counterpart. Effects such as scattering efficiency
and shape of the nanowire's cross section are also discussed.Comment: 5 pages, 3 figures. Comments are welcom
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