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Dynamic response of one-dimensional interacting fermions
We evaluate the dynamic structure factor of interacting
one-dimensional spinless fermions with a nonlinear dispersion relation. The
combined effect of the nonlinear dispersion and of the interactions leads to
new universal features of . The sharp peak , characteristic for the Tomonaga-Luttinger model, broadens
up; for a fixed becomes finite at arbitrarily large .
The main spectral weight, however, is confined to a narrow frequency interval
of the width . At the boundaries of this interval the
structure factor exhibits power-law singularities with exponents depending on
the interaction strength and on the wave number
Swing switching of spin-torque valves
We propose a method for inducing magnetization reversal using an AC spin
current polarized perpendicular to the equilibrium magnetization of the free
magnetic layer. We show that the critical AC spin current is significantly
smaller than the corresponding DC one. The effect is understood as a
consequence of the underdamped nature of the spin-torque oscillators. It allows
to use the kinetic inertia to overcome the residual energy barrier, rather than
suppressing the latter by a large spin current. The effect is similar to a
swing which may be set into high amplitude motion by a weak near-resonant push.
The optimal AC frequency is identified as the upper bifurcation frequency of
the corresponding driven nonlinear oscillator. Together with fast switching
times it makes the perpendicular AC method to be the most efficient way to
realize spin-torque memory valve.Comment: 8 pages, 11 figure
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