3 research outputs found
Cooling of a suspended nanowire by an AC Josephson current flow
We consider a nanoelectromechanical Josephson junction, where a suspended
nanowire serves as a superconducting weak link, and show that an applied DC
bias voltage an result in suppression of the flexural vibrations of the wire.
This cooling effect is achieved through the transfer of vibronic energy quanta
first to voltage driven Andreev states and then to extended quasiparticle
electronic states. Our analysis, which is performed for a nanowire in the form
of a metallic carbon nanotube and in the framework of the density matrix
formalism, shows that such self-cooling is possible down to a level where the
average occupation number of the lowest flexural vibration mode of the nanowire
is .Comment: 4 pages, 3 figure
Voltage-driven superconducting weak link as a refrigerator for cooling of nanomechanical vibrations
We consider a new type of cooling mechanism for a suspended nanowire acting
as a weak link between two superconductive electrodes. By applying a bias
voltage over the system, we show that the system can be viewed as a
refrigerator for the nanomechanical vibrations, where energy is continuously
transferred from the vibrational degrees of freedom to the extended
quasiparticle states in the leads through the periodic modulation of the
inter-Andreev level separation. The necessary coupling between the electronic
and mechanical degrees of freedom responsible for this energy-transfer can be
achieved both with an external magnetic or electrical field, and is shown to
lead to an effective cooling of the vibrating nanowire. Using realistic
parameters for a suspended nanowire in the form of a metallic carbon nanotube
we analyze the evolution of the density matrix and demonstrate the possibility
to cool the system down to a stationary vibron population of .
Furthermore, it is shown that the stationary occupancy of the vibrational modes
of the nanowire can be directly probed from the DC current responsible for
carrying away the absorbed energy from the vibrating nanowire.Comment: 10 pages, 4 figure
Dynamics of a suspended nanowire driven by an ac Josephson current in an inhomogeneous magnetic field
We consider a voltage-biased nanoelectromechanical Josephson junction, where
a suspended nanowire forms a superconducting weak-link, in an inhomogeneous
magnetic field. We show that a nonlinear coupling between the Josephson current
and the magnetic field generates a Laplace force that induces a whirling motion
of the nanowire. By performing an analytical and a numerical analysis, we
demonstrate that at resonance, the amplitude-phase dynamics of the whirling
movement present different regimes depending on the degree of inhomogeneity of
the magnetic field: time independent, periodic and chaotic. Transitions between
these regimes are also discussed.Comment: 7 pages, 5 figure