2,163 research outputs found
Classical Phase Space Revealed by Coherent Light
We study the far field characteristics of oval-resonator laser diodes made of
an AlGaAs/GaAs quantum well. The resonator shapes are various oval geometries,
thereby probing chaotic and mixed classical dynamics. The far field pattern
shows a pronounced fine structure that strongly depends on the cavity shape.
Comparing the experimental data with ray-model simulations for a Fresnel
billiard yields convincing agreement for all geometries and reveals the
importance of the underlying classical phase space for the lasing
characteristics.Comment: 4 pages, 5 figures (reduced quality), accepted for publication in
Physical Review Letter
Scaling Theory of Giant Frictional Slips in Decompressed Granular Media
When compressed frictional granular media are decompressed, generically a
fragile configuration is created at low pressures. Typically this is
accompanied by a giant frictional slippage as the fragile state collapses. We
show that this instability is understood in terms of a scaling theory with
theoretically computable amplitudes and exponents. The amplitude diverges in
the thermodynamic limit hinting to the possibility of huge frictional slip
events in decompressed granular media. The physics of this slippage is
discussed in terms of the probability distribution functions of the tangential
and normal forces on the grains which are highly correlated due to the Coulomb
condition.Comment: 5 pages, 5 figures. arXiv admin note: text overlap with
arXiv:1804.0771
Microscopic Mechanism of Shear Bands in Amorphous Solids
The fundamental instability responsible for the shear localization which
results in shear bands in amorphous solids remains unknown despite enormous
amount of research, both experimental and theoretical. As this is the main
mechanism for the failure of metallic glasses, understanding the instability is
invaluable in finding how to stabilize such materials against the tendency to
shear localize. In this Letter we explain the mechanism for shear localization
under shear, which is the appearance of highly correlated lines of Eshelby-like
quadrupolar singularities which organize the non-affine plastic flow of the
amorphous solid into a shear band. We prove analytically that such highly
correlated solutions in which \C N quadrupoles are aligned with equal
orientations are minimum energy states when the strain is high enough. The line
lies at 45 degrees to the compressive stress
Plasticity-Induced Magnetization in Amorphous Magnetic Solids
Amorphous magnetic solids, like metallic glasses, exhibit a novel effect: the
growth of magnetic order as a function of mechanical strain under athermal
conditions in the presence of a magnetic field. The magnetic moment increases
in steps whenever there is a plastic event. Thus plasticity induces the
magnetic ordering, acting as the effective noise driving the system towards
equilibrium. We present results of atomistic simulations of this effect in a
model of a magnetic amorphous solid subjected to pure shear and a magnetic
field. To elucidate the dependence on external strain and magnetic field we
offer a mean-field theory that provides an adequate qualitative understanding
of the observed phenomenon
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