1,484 research outputs found
Quantum Fokker-Planck models: the Lindblad and Wigner approaches
In this article we try to bridge the gap between the quantum dynamical
semigroup and Wigner function approaches to quantum open systems. In particular
we study stationary states and the long time asymptotics for the quantum
Fokker-Planck equation. Our new results apply to open quantum systems in a
harmonic confinement potential, perturbed by a (large) sub-quadratic term.Comment: 19 pages, corrected typos and quoted Theorem 6 more precisel
Ultra-low switching current density in all-amorphous W-Hf / CoFeB / TaOx films
We study current-induced deterministic magnetization switching and domain
wall motion via polar Kerr microscopy in all-amorphous
WHf/CoFeB/TaO with perpendicular magnetic anisotropy
and large spin Hall angle. Investigations of magnetization switching as a
function of in-plane assist field and current pulse-width yield switching
current densities as low as A/m. We accredit this low
switching current density to a low depinning current density, which was
obtained from measurements of domain wall displacements upon current injection.
This correlation is verified by investigations of a Ta/CoFeB/MgO/Ta reference
sample, which showed critical current densities of at least one order of
magnitude larger, respectively.Comment: 9 pages, 8 figure
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