950 research outputs found
Large current noise in nanoelectromechanical systems close to continuous mechanical instabilities
We investigate the current noise of nanoelectromechanical systems close to a
continuous mechanical instability. In the vicinity of the latter, the
vibrational frequency of the nanomechanical system vanishes, rendering the
system very sensitive to charge fluctuations and, hence, resulting in very
large (super-Poissonian) current noise. Specifically, we consider a suspended
single-electron transistor close to the Euler buckling instability. We show
that such a system exhibits an exponential enhancement of the current noise
when approaching the Euler instability which we explain in terms of telegraph
noise.Comment: 11 pages, 12 figures; v2: minor changes, published versio
Coherent magnetization precession in ferromagnetic (Ga,Mn)As induced by picosecond acoustic pulses
We show that the magnetization of a thin ferromagnetic (Ga,Mn)As layer can be
modulated by picosecond acoustic pulses. In this approach a picosecond strain
pulse injected into the structure induces a tilt of the magnetization vector M,
followed by the precession of M around its equilibrium orientation. This effect
can be understood in terms of changes in magneto-crystalline anisotropy induced
by the pulse. A model where only one anisotropy constant is affected by the
strain pulse provides a good description of the observed time-dependent
response.Comment: 13 pages, 3 figure
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