Photon Heat Transport In Mesoscopic Josephson Devices

With the development of integration of electric devices,due to the critical position of the thermal problems,the thermal transportion issues walk into the sight of scientists.This thesis focuses on the heat current of mesoscopic Josephson junction(MJJ)which coupled with photon reservoirs.We use the non-equilibrium Green’s function method to explor heat current of the systems.Besides,we consider the heat current under the influence of different parameters.In the first chapter,the background and current research satus of MJJ is discussed.Then the non-equilibrium Green’s function method is introduced in chapter 2.The main researches are arranged in chapter 3,4,5.Development of this field is metioned in the last.First of all,we are interested in the photon heat current of dc voltage biasd MJJ which coupled with two photon resevoirs.The Landauer-like formulas of photon heat current have been derived in both Fourier space and its time-oscillating version,where Coulomb interaction,self inductance,and magnetic flux are involved in.The nonlinear effects are involved in the photon heat current due to the quantum nature of MJJ and applied external dc voltage.The obtained oscillation structure of heat current is a superposition of oscillations with various periods.Magnitude of the heat current decreases with increasing the dc bias,and period of the heat current also controlled by the external dc bias.The heat current also can be adjusted by turning the magnetic field at definite bias,so the heat current can be translated to an expecting value by changing the dc bias.Secondly,in order to exploring heat current properties of MJJ devices,dc and ac voltages are biased on the MJJ.Ac bias generates additional oscillating supercurrent in the supercontor ring,which contains the combination of infinity ac current branches.The photon heat current is determined by the suoerposition of differnet heat current branches.Calderira-Leggett circuit theory has been used to deal with the resevoirs and central device into circuit parts.Non-equilibrium Green’s function method is employed to derive the photon heat current,time-averaged heat current,differential heat conductance fomulars.We find that Josephson frequency which is induced by the dc bias,the frequency of ac voltage,magnitude of ac voltage are three very important factors in controlling the photon heat current.Specially,the ratio between Josephson frequency and the frequency of ac voltage takes an effect part in controlling the photon heat current and heat conductance.Meanwhile,turn the value of the ratio and the value of Coulomb energy to meat some matching beat-like resonance occurs.Finally,thermal characteristics of two series coupled MJJ ring are studied.Dc voltages are applied on two MJJ seperatly.Obtained time-oscillating photon heat current contains nonlinear behaviors,and the nonlinear behaviors are under the control of external biases.The investigation shows that heat current oscillates with time periodically contributed by the superpositon of photon heat current branches associated with Josephson frequcncies of MJJs.Nonlinear behaviors are exhibited to be induced by the self-inductance,Coulomb interactions,and interference effect relating to the coherent transport of Cooper pairs in the MJJs.Josephson frequcncies of MJJs and Coulomb interactions decides the detailed configuration of heat current together.Time-oscillating pumping photon heat current is generated in the absence of temperature difference.In a word,this thsis deals with the photon heat current through mesoscopic devices which coupled photon reservoirs.When we obtain the expressions of the systems,we try many ways to moludate the photon heat current of the systems by changing the different parameters.And we get some methods to control the photon heat current of MJJ,by which we can obtain expected heat current.