127 research outputs found
Sound modes in composite incommensurate crystals
We propose a simple phenomenological model describing composite crystals,
constructed from two parallel sets of periodic inter-penetrating chains. In the
harmonic approximation and neglecting thermal fluctuations we find the
eigenmodes of the system. It is shown that at high frequencies there are two
longitudinal sound modes with standard attenuation, while in the low frequency
region there is one propagating sound mode and an over-damped phase mode. The
crossover between these two regions is analyzed numerically and the dynamical
structure factor is calculated. It is shown that the qualitative features of
the experimentally observed spectra can be consistently described by our model.Comment: 12 pages, 2 eps figures, Revtex, accepted to European Physics Journal
B, (2002
Laser Pulse Heating of Spherical Metal Particles
We consider a general problem of laser pulse heating of spherical metal
particles with the sizes ranging from nanometers to millimeters. We employ the
exact Mie solutions of the diffraction problem and solve heat-transfer
equations to determine the maximum temperature at the particle surface as a
function of optical and thermometric parameters of the problem. The main
attention is paid to the case when the thermometric conductivity of the
particle is much larger than that of the environment, as it is in the case of
metal particles in fluids. We show that in this case at any given finite
duration of the laser pulse the maximum temperature rise as a function of the
particle size reaches an absolute maximum at a certain finite size of the
particle, and we suggest simple approximate analytical expressions for this
dependence which covers the entire range of variations of the problem
parameters and agree well with direct numerical simulations.Comment: 7 pages, 6 figure
Optical generation of intense ultrashort magnetic pulses at the nanoscale
Generating, controlling and sensing strong magnetic fields at ever shorter time and length scales is important for both fundamental solid-state physics and technological applications such as magnetic data recording. Here, we propose a scheme for producing strong ultrashort magnetic pulses localized at the nanoscale. We show that a bimetallic nanoring illuminated by femtosecond laser pulses responds with transient thermoelectric currents of picosecond duration, which in turn induce Tesla-scale magnetic fields in the ring cavity. Our method provides a practical way of generating intense nanoscale magnetic fields with great potential for materials characterization, terahertz radiation generation and data storage applications
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