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Thomas Unnerstall 《Journal of statistical physics》1989,54(1-2):379-403
The irreversible macroscopic dynamics of the Josephson junction coupled to external wires acting as a current source is derived rigorously from the underlying microscopic Hamiltonian quantum mechanics. The external systems are treated in the singular coupling limit. The use of this limit is explicitly justified via an interpretation of the singular coupling limit in terms of the relative magnitudes of system, reservoir, and coupling energies. The qualitative behavior of the macroscopic dynamical equations is shown to depend sensitively and crucially on the interaction between the wires and the superconductors and on the size of the wires: the dc Josephson effect only happens when one lets Cooper pairs be driven into the junction by collective (i.e., small) reservoirs. 相似文献
3.
4.
The enhanced low-dose-rate sensitivity (ELDRS) and dose-rate dependence of vertical NPN transistors are investigated in this article.The results show that the vertical NPN transistors exhibit more degradation at low dose rate,and that this degradation is attributed to the increase on base current.The oxide trapped positive charge near the SiO2-Si interface and interface traps at the interface can contribute to the increase on base current and the two-stage hydrogen mechanism associated with space charge effect can well explain the experimental results. 相似文献
5.
An ab initio analysis of the periodic array of Au/Si nanostructure composed of gold clusters linked to silicon quantum dot (QD) co-doped by aluminium and phosphorus along [111] direction is presented in this paper. The density functional theory (DFT) is used to compute the electronic structure of the simulated system. Non-adiabatic coupling implemented in the form of dissipative equation of motion for reduced density matrix is used to study the phonon-induced relaxation in the simulated system. The density of states clearly shows that the formation of Au–Si bonds contributes states to the band gap of the model. Dynamics of selected photo-excitations shows that hole relaxation in energy and in space is much faster than electron relaxation, which is due to the higher density of states of the valence band. 相似文献
6.
Two distinct Josephson junctions (JJs) connected with a constant coupling resistance Rcp are theoretically considered to investigate the overall dynamics below and above the critical current Ic. The circuit model of the device is driven by two DC current sources, I1 and I2. Each junction is characterized by a nonlinear resistive–capacitive junction (NRCSJ). Having constructed the circuit model, time-dependent simulations are carried out for a variety of control parameter sets. Common techniques such as bifurcation diagrams, two-dimensional attractors and Lyapunov exponents are applied for the determination of chaotic as well as periodic dynamics of the superconducting junction devices. According to the findings, two states (namely superconducting and ordinary conducting) are determined as functions of the source currents. The chaotic current which flows through Rcp exhibits a very rich behavior depending on the source currents I1 and I2 and junction capacitances C1 and C2. The device characteristics are summarized by a number of three-dimensional phase diagrams in the parameter space. In addition, for certain parameters, hyper-chaotic cases with two positive Lyapunov exponents are encountered. In contrast to earlier studies claiming the need for a sinusoidal feeding current for generating a chaotic signal, our circuitry can easily generate one via a DC source. 相似文献
7.
The resistance switching behavior has recently attracted great attentions for its application as resistive random access memories (RRAMs) due to a variety of advantages such as simple structure, high-density, high-speed and low-power. As a leading storage media, the transition metal perovskite oxide owns the strong correlation of electrons and the stable crystal structure, which brings out multifunctionality such as ferroelectric, multiferroic, superconductor, and colossal magnetoresistance/electroresistance effect, etc. The existence of rich electronic phases, metal–insulator transition and the nonstoichiometric oxygen in perovskite oxide provides good platforms to insight into the resistive switching mechanisms. 相似文献
8.
《Physics letters. A》2020,384(32):126826
In this paper, hydrogenation is used for the generation of band gap in silicene and the hydrogenated silicene is then studied for its spintronic application. Upon hydrogenation, silicene transforms into a wide band gap material with a band gap of 3.32 eV. Parameters like magneto-resistance and spin-filtering efficiency of magnetic tunnel junction (MTJ) with CrO2 as semi-metallic electrodes and hydrogenated silicene as scattering region are found to increase compared to pristine silicene as scattering region. The simulation results show that the magneto-resistance of hydrogenated silicene remains above 85% (higher than the pristine counterpart) for the entire bias range. In addition, the spin-filtering efficiency in hydrogenated silicene reaches a value as high as 96% whereas in case of pristine silicene it remains below 90% for the entire bias range. 相似文献
9.
The possibility of cooling a system from liquid helium temperature,
4.2~K, using a tunnel junction refrigerator is analysed. Calculations
show that the device can be used over a wide temperature range from
4~K down to well below 1~mK with necessary cooling power. However,
several serious difficulties must be overcome before the method can
be used in low temperature laboratories. 相似文献
10.
S.G. ChigarevE.M. Epshtein P.E. Zilberman 《Journal of magnetism and magnetic materials》2011,323(1):130-132
A tunnel magnetic junction is considered with magnetic hard and magnetic soft layers of cubic symmetry. The magnetic switching of the layers is analyzed for a magnetic field perpendicular to the initial magnetizations. In such a situation, an additional peak in the tunnel magnetoresistance ratio appears at the magnetic field value that is substantially lower than the anisotropy field of the soft layer. 相似文献