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Ground state cooling of a carbon nano-mechanical resonator by spin-polarized current

We study the non-equilibrium regime of a mechanical resonator at low temperature realized with a suspended carbon nanotube quantum dot contacted to two ferromagnets. Due to spin- orbit interaction and/or an external magnetic gradient, the spin on the dot couples directly to the flexural eigenmodes. Owing to this interaction, the nanomechanical motion induces spin-flips of the electrons passing through the nanotube. When a finite voltage is applied, a spin-polarized current causes either heating…

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"Smile"-gap in the density of states of a cavity between superconductors

The density of Andreev levels in a normal metal (N) in contact with two superconductors (S) is known to exhibit an induced minigap related to the inverse dwell time. We predict a small secondary gap just below the superconducting gap edge - a feature that has been overlooked so far in numerous microscopic studies of the density of states in SNS structures. In a generic structure with N being a chaotic cavity, the secondary gap is the widest at zero phase bias. It closes at some finite phase…