engleski

Coulomb-promoted mechanics in magnetic shuttle NEMS

We address the role of Coulomb interactions (Coulomb blockade) leading to electromechanical instability in magnetic NEMS consisting of spin-resolved nanosized metallic grain (shuttle) between magnetic leads (S, D) with opposite magnetizations, biased to different chemical potentials mu_S, D. Perpendicular external magnetic field H regulates population of spin-up/down state in the shuttle (spin "rotation") while Coulomb interaction energy U on the grain regulates its double occupation (parity). The driving force for mechanical motion, and consequently the instability leading to self-excited oscillations, is magnetic exchange force from the leads acting on the spin on the shuttle provided by the electron tunneling events from the leads with rates G_S, G_D. Starting from the strict quantum density matrix approach, we demonstrate the Coulomb-promoted electromechanical instability in the proposed NEMS showing approximately linear dependence of critical strength of Coulomb interaction U_C on temperature T, i.e. U_C = T ln[G_S/(G_D*n_c)], where n_c is the ratio of stationary populations of spin-double and spin-down on the shuttle in the crossover regime of instability development.

nanoelectromechanical systems, Coulomb blockade, shuttle

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