We study the heat generation by an electric current in a quantum dot （QD） molecular coupled to a single-model phonon bath in the Coulomb blockade regime. It is found that when the system is driven out of equilibrium...We study the heat generation by an electric current in a quantum dot （QD） molecular coupled to a single-model phonon bath in the Coulomb blockade regime. It is found that when the system is driven out of equilibrium by the thermal bias applied across the two terminals of the structure, the heat flowing between the QD and the phonon bath can be very small for one direction of the thermal bias, while it becomes quite large when the corresponding direction of the thermal bias is reversed. The device thus operates as a heat rectifier or heat diode. Moreover, the heat generation can be suppressed to negative values by the thermal bias. We emphasize that the above-mentioned two effects are beyond the reach of the usual electric bias.展开更多
We study electronic spin-polarised transport in a system composed of a quantum dot(QD)connected to one normal metal electrode and one ferromagnetic one.The electrical current of each spin component and the spin accumu...We study electronic spin-polarised transport in a system composed of a quantum dot(QD)connected to one normal metal electrode and one ferromagnetic one.The electrical current of each spin component and the spin accumulation on the QD are calculated by using the nonequilibrium Green's function method.We find that in the Coulomb blockade regime,the current spin polarisation can reach 100%under a strong magnetic field.Meanwhile,the spin accumulation on the QD approaches to unit,and thus the dot is occupied by electrons of one certain spin orientation.The system can operate as a spin injector from a normal metal reservoir to a semiconductor material,and may find real usage in solid state quantum information processes.展开更多
Double-sided superconducting MgB2 thin films are deposited onto c-A120a substrates by the hybrid physical chemical vapour deposition method. The microwave response of MgB2/A12O3 is investigated by microstrip resonator...Double-sided superconducting MgB2 thin films are deposited onto c-A120a substrates by the hybrid physical chemical vapour deposition method. The microwave response of MgB2/A12O3 is investigated by microstrip resonator technique. A grain-size model is introduced to the theory of microstrip resonators to analyse microwave properties of the films. We obtain effective penetration depth of the films at OK （λe0 = 463nm） and surface resistance （R8 = 1.52 mΩ at 11 K and 8. 73 GHz） by analysing the resonant frequency and unload quality factor of the microstrip resonator, which suggests that the impurities and disorders of grain boundaries of MgB2/A12 Oa result in increasing penetration depth and surface resistance of the films.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 61274101.
文摘We study the heat generation by an electric current in a quantum dot （QD） molecular coupled to a single-model phonon bath in the Coulomb blockade regime. It is found that when the system is driven out of equilibrium by the thermal bias applied across the two terminals of the structure, the heat flowing between the QD and the phonon bath can be very small for one direction of the thermal bias, while it becomes quite large when the corresponding direction of the thermal bias is reversed. The device thus operates as a heat rectifier or heat diode. Moreover, the heat generation can be suppressed to negative values by the thermal bias. We emphasize that the above-mentioned two effects are beyond the reach of the usual electric bias.
基金Supported by the National Natural Science Foundation of China under Grant No 61274101Program for Liaoning Excellent Talents in University under Grant No 2009R01.
文摘We study electronic spin-polarised transport in a system composed of a quantum dot(QD)connected to one normal metal electrode and one ferromagnetic one.The electrical current of each spin component and the spin accumulation on the QD are calculated by using the nonequilibrium Green's function method.We find that in the Coulomb blockade regime,the current spin polarisation can reach 100%under a strong magnetic field.Meanwhile,the spin accumulation on the QD approaches to unit,and thus the dot is occupied by electrons of one certain spin orientation.The system can operate as a spin injector from a normal metal reservoir to a semiconductor material,and may find real usage in solid state quantum information processes.
基金Supported by the National Natural Science Foundation of China under Grant No 10174006.
文摘Double-sided superconducting MgB2 thin films are deposited onto c-A120a substrates by the hybrid physical chemical vapour deposition method. The microwave response of MgB2/A12O3 is investigated by microstrip resonator technique. A grain-size model is introduced to the theory of microstrip resonators to analyse microwave properties of the films. We obtain effective penetration depth of the films at OK （λe0 = 463nm） and surface resistance （R8 = 1.52 mΩ at 11 K and 8. 73 GHz） by analysing the resonant frequency and unload quality factor of the microstrip resonator, which suggests that the impurities and disorders of grain boundaries of MgB2/A12 Oa result in increasing penetration depth and surface resistance of the films.
