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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-23 18:00 |
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Conference: Bucharest University Faculty of Physics 2017 Meeting
Section: Solid State Physics and Materials Science
Title:
Vibronic signatures in open nanoelectromechanical systems
Authors:
Stefan STANCIU (1,2)
Affiliation:
1) Facultatea de fizica, Univ. Bucuresti
2) National Institute of Materials Physics
E-mail
stefanbstanciu@gmail.com
Keywords:
NEMS, vibrons, open quantum systems, standard quantum limit
Abstract:
Recently, nanoelectromechanical systems (NEMS) captured the attention from both theoretical and experimental point of view. One can construct such a device by bringing in the vicinity of a mesoscopic system( a quantum dot-QD, for example) a nanoresonator (NR). This NR could be a carbon nanotube which has the resonance frequency in the MHz domain. On the other side, the QD is weakly coupled, by tunnel junctions, to two metalic contacts, between these 2 contacts a constant potential drop is kept (the source and drain contacts). The NR is capacitatively coupled to the QD, the interaction between these 2 components depends both on the nanoresonator position and the electronic occupation of the dot. The effects of this interaction were theoretically predicted and experimentally measured. The reduction of the tunneling current for weak electro-machanical interaction- the Franck-Condon blockade is an example. These systems are theoretically described in the Andreson-Holstein model, the QD keeps only a single level. From the open quantum systems point of view (the metalic leads play the role of a reservoir, the system of interest being the ensamble QD-NR) the time evolution of the reduced statistical operator is deduced from a Master equation in Born and Markov approximations. Taking into account the relation between the measured current and the NR displacement, one can conclude that these devices could be used to indirectly find very small distances, close to the standard quantum limit. For these to be achieved NEMS must operate in the quantum regime which implies ultralow temperatures, down to few mK, that is the main technical task in order that these devices could operate.
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