1,011 research outputs found
What are the left-handed media and what is interesting about them?
We review the intensively discussed ideas about wave propagation and
refraction in media where both electric permittivity and magnetic permeability
are negative. The criticism against negative refraction as violating the
causality principle is considered. Starting from the initial wave equations,
refraction of beams at the boundary of a left-handed medium is analyzed. The
physics of a perfect lens formed by a flat layer of a left-handed material is
considered.Comment: 21 pages, 8 figure
Topological spin transport of photons: the optical Magnus Effect and Berry Phase
The paper develops a modified geometrical optics (GO) of smoothly
inhomogeneous isotropic medium, which takes into account two topological
phenomena: Berry phase and the optical Magnus effect. By using the analogy
between a quasi-classical motion of a quantum particle with a spin and GO of an
electromagnetic wave in smoothly inhomogeneous media, we have introduced the
standard gauge potential associated with the degeneracy in the wave momentum
space. This potential corresponds to the Dirac-monopole-like field (Berry
curvature), which causes the topological spin (polarization) transport of
photons. The deviations of waves of right-hand and left-hand helicity occur in
the opposite directions and orthogonally to the principal direction of motion.
This produces a spin current directed across the principal motion. The
situation is similar to the anomalous Hall effect for electrons. In addition, a
simple scheme of the experiment allowing one to observe the topological spin
splitting of photons has been suggested.Comment: 4 pages, 1 figur
Paraxial spin transport using the Dirac-like paraxial wave equation
In weakly inhomogeneous media, Maxwell equations assume a Dirac-like form
that is particularly apt for the study of paraxial propagation. Using this
form, and via the Foldy-Wouthuysen transformation technique of the Dirac
equation, we study the spin transport of paraxial light beams in weakly
inhomogeneous media. We derive the Berry effect terms and establish the spin
Hall effect and the Rytov rotation law for polarized paraxial beam transport.Comment: To appear in Phys. Lett. A (2010
Geometrodynamics of polarized light: Berry phase and spin Hall effect in a gradient-index medium
We review the geometrical-optics evolution of an electromagnetic wave
propagating along a curved ray trajectory in a gradient-index dielectric
medium. A Coriolis-type term appears in Maxwell equations under transition to
the rotating coordinate system accompanying the ray. This term describes the
spin-orbit coupling of light which consists of (i) the Berry phase responsible
for a trajectory-dependent polarization variations and (ii) the spin Hall
effect representing polarization-dependent trajectory perturbations. These
mutual phenomena are described within universal geometrical structures
underlying the problem and are explained by the dynamics of the intrinsic
angular momentum carried by the wave. Such close geometro-dynamical
interrelations illuminate a dual physical nature of the phenomena.Comment: 25 pages, 4 figures, review to appear in special issue of J. Opt. A:
Pure Appl. Op
On the Hamiltonian nature of semiclassical equations of motion in the presence of an electromagnetic field and Berry curvature
We consider the semiclassical equations of motion of a particle when both an
external electromagnetic field and the Berry gauge field in the momentum space
are present. It is shown that these equations are Hamiltonian and relations
between the canonical and covariant variables are determined through a
consistent account of all components of the Berry connection. The Jacobian of
the canonical-to-covariant-variables transformation describes the
nonconservation of the 'naive' phase space volume in the covariant coordinates
(D.Xiao, J.Shi, and Q.Niu, Phys. Rev. Lett. 95, 137204 (2005)).Comment: 3 pages, to appear in Physics Letters
On spin evolution in a time-dependent magnetic field: post-adiabatic corrections and geometric phases
We examine both quantum and classical versions of the problem of spin
evolution in a slowly varying magnetic field. Main attention is given to the
first- and second-order adiabatic corrections in the case of in-plane
variations of the magnetic field. While the first-order correction relates to
the adiabatic Berry phase and Coriolis-type lateral deflection of the spin, the
second-order correction is shown to be responsible for the next-order geometric
phase and in-plain deflection. A comparison between different approaches,
including the exact (non-adiabatic) geometric phase, is presented.Comment: 10 pages, 1 figure, to appear in Phys. Lett.
Spin and orbital angular momenta of acoustic beams
We analyze spin and orbital angular momenta in monochromatic acoustic wave
fields in a homogeneous medium. Despite being purely longitudinal (curl-free),
inhomogeneous acoustic waves generically possess nonzero spin angular momentum
density caused by the local rotation of the vector velocity field. We show that
the integral spin of a localized acoustic wave vanishes in agreement with the
spin-0 nature of longitudinal phonons. We also show that the helicity or
chirality density vanishes identically in acoustic fields. As an example, we
consider nonparaxial acoustic Bessel beams carrying well-defined integer
orbital angular momentum, as well as nonzero local spin density, with both
transverse and longitudinal components. We describe the nontrivial polarization
structure in acoustic Bessel beams and indicate a number of observable
phenomena, such as nonzero energy density and purely-circular transverse
polarization in the center of the first-order vortex beams.Comment: 15 pages, 3 figures, 1 table, to appear in Phys. Rev.
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