| 1. |
- Bahrova, O. M., et al.
(author)
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Cooling of nanomechanical vibrations by Andreev injection
- 2022
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In: Low Temperature Physics. - : AIP Publishing. - 1063-777X .- 1090-6517. ; 48:6, s. 476-482
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Journal article (peer-reviewed)abstract
- A nanoelectromechanical weak link composed of a carbon nanotube suspended between two normal electrodes in a gap between two superconducting leads is considered. The nanotube is treated as a movable single level quantum dot in which the position-dependent superconducting order parameter is induced due to the Cooper pair tunneling. We show that electron tunneling processes significantly affect the state of the mechanical subsystem. We found that at a given direction of the applied voltage between the electrodes, the stationary state of the mechanical subsystem has a Boltzmann form with an effective temperature dependent on the parameters of the device. As this takes place, the effective temperature can reach significantly small values (cooling effect). We also demonstrate that nanotube fluctuations strongly affect the dc current through the system. The latter can be used to probe the predicted effects in an experiment. Published under an exclusive license by AIP Publishing.
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| 2. |
- Bahrova, O. M., et al.
(author)
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Entanglement between charge qubit states and coherent states of nanomechanical resonator generated by ac Josephson effect
- 2021
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In: Low Temperature Physics. - : AIP Publishing. - 1063-777X .- 1090-6517. ; 47:4, s. 287-293
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Journal article (peer-reviewed)abstract
- We considered a nanoelectromechanical system consisting of a movable Cooper-pair box qubit, which is subject to an electrostatic field, and coupled to the two bulk superconductors via tunneling processes. We suggest that qubit dynamics is related to that of a quantum oscillator and demonstrate that a bias voltage applied between superconductors generates states represented by the entanglement of qubit states and coherent states of the oscillator if certain resonant conditions are fulfilled. It is shown that a structure of this entanglement may be controlled by the bias voltage in a way that gives rise to the entanglement incorporating so-called cat-states—the superposition of coherent states. We characterize the formation and development of such states analyzing the entropy of entanglement and corresponding Wigner function. The experimentally feasible detection of the effect by measuring the average current is also considered.
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| 3. |
- Bahrova, O. M., et al.
(author)
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Nanomechanics driven by the superconducting proximity effect
- 2022
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In: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 24:3
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Journal article (peer-reviewed)abstract
- We consider a nanoelectromechanical weak link composed of a carbon nanotube suspended above a trench in a normal metal electrode and positioned in a gap between two superconducting leads. The nanotube is treated as a movable single-level quantum dot (QD) in which the position-dependent superconducting order parameter is induced as a result of Cooper pair tunneling. We show that in such a system, self-sustained bending vibrations can emerge if a bias voltage is applied between normal and superconducting electrodes. The occurrence of this effect crucially depends on the direction of the bias voltage and the relative position of the QD level. We also demonstrate that the nanotube vibrations strongly affect the dc current through the system, a characteristic that can be used for the direct experimental observation of the predicted phenomenon.
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