Spin Dynamical Investigation Of Micro-nano Mechanical System

With the development of science and technology, because of its tiny size andshape、tiny operating scale characteristics, micromechanics has became a high andnew technology from which people can understand and transform the objective worldfrom the micro perspective. In recent years, micro-nano scale mechanical resonatorhas became a new research hotspot due to its many important characteristics andapplications. One of the most attractive、the most promising mechanical resonators isthe resonant micro mechanical resonator, With the development of science andtechnology, this kind of resonator is expected to be widely used in making the nanoprobe, the key device fabrication of chemical sensors、wireless communication andoptical wireless communication system and another various fields. In this paper, bysolving the master equation, we mainly studied the dynamic research between Spinand Carbon Nano-tube Resonator under Strong Coupling, and Dynamical dissipativecooling of a cavity opto-mechanical oscillator. The research content and conclusionsare as follows:1、The dynamic behavior of system which influenced by the coupling betweenthe single electron spin and carbon nano-tube mechanical resonator is theoreticallyanalyzed.By means of a master equation, average phonon occupation number asfunctions of the frequency detuning under the case with and without qubit-oscillatorcoupling is investigated via a semiclassical approach、the variation of average phononoccupation number as functions of the frequency detuning under the case with andwithout rotating-wave approximation is compared for different coupling strength. Forcoupling system, average phonon occupation number occurs a splitting phenomenmonwhen resonance, simultaneously, a bistable state is observed near the splitting peak.By analyzing the average phonon occupation number of the carbon nanotubesresonator, it finds that rotating-wave approximation and non-rotating-waveapproximation can coincide with each other very well under the weak couplingstrength. However, the non-rotating-wave approximation term must be considered inthe ultrastrong coupling system due to the rotating-wave approximation is no longereffective.2、The dynamical cooling process of a cavity opto-mechanical system isinvestigated theoretically by a master equation. The mean phonon number is calculated using the covariance approach. Firstly, the effect of different cavitydissipation rate on the mean phonon number is discussed in the strong couplingsystem. Then the variation of mean phonon number changing with differentparameters in the weak and strong coupling system is compared. In the strongcoupling system, in a certain range, the higher the cavity dissipation rate, the smallerthe mean phonon number, that is to say, by increasing the cavity dissipation rate, wecan accelerate the cooling process of the system. For strong coupling regime, themean phonon number oscillates periodically as the increase of coupling strength and itdecreases fast as the cavity dissipation rate increases. Finally, it reaches a coolinglimit. On the contrary, in the weak coupling regime, the mean phonon numberincreases fast as the cavity dissipation rate increases and it reaches equilibrium in theend.