Quantum pump effect in a four-terminal mesoscopic structure constructed from a homogeneous two- dimensional electron gas is investigated. Oscillating electric potentials are applied to the two opposite terminals of th...Quantum pump effect in a four-terminal mesoscopic structure constructed from a homogeneous two- dimensional electron gas is investigated. Oscillating electric potentials are applied to the two opposite terminals of the four-terminal mesoscopic structure. In both the remaining two opposite terminals and in the central region there are constant potentials that do not change with time. The oscillating potentials change slowly in comparison with all of the internal time scales of the structure and the amplitude of the oscillating potentials is small in comparison with the Fermi energy. The current of each lead and the transmission coefficients from one lead to another are calculated by using the non-equilibrium Green＇s function approach under the adiabatic approximation. In the remaining two opposite terminals of the four-terminal structure, the quantum pump effect can produce an electric current whose magnitude and direction depends on the Fermi energy. The pumped currents are ascribed to the asymmetry of transmission coefficients with respect to the Fermi energy.展开更多
Based on the scattering matrix approach.we systematically investigate the anharmonic effect of the pumped current in double-barrier strructures with adiabatic time-modulation of two sinusoidal AC driven potential he...Based on the scattering matrix approach.we systematically investigate the anharmonic effect of the pumped current in double-barrier strructures with adiabatic time-modulation of two sinusoidal AC driven potential heights. The pumped currem as a functionof the pha.se difference bet ween the two driven potentials looks like to be sinusoidal, but actually it contains sine functions of double and more phase difference, it is found that this kind of anharmonic effect of the pumped current is determined combinedly by the Berry curvature and parameter va.riation loop trajectory. Therefore small ratio of the driving amplitude and the static amplitude is not necessary for harmonic pattern in the pmnped era＇rent, to dominate for smooth Berry curvatureon the surface within the parameter variation loop.展开更多
文摘Quantum pump effect in a four-terminal mesoscopic structure constructed from a homogeneous two- dimensional electron gas is investigated. Oscillating electric potentials are applied to the two opposite terminals of the four-terminal mesoscopic structure. In both the remaining two opposite terminals and in the central region there are constant potentials that do not change with time. The oscillating potentials change slowly in comparison with all of the internal time scales of the structure and the amplitude of the oscillating potentials is small in comparison with the Fermi energy. The current of each lead and the transmission coefficients from one lead to another are calculated by using the non-equilibrium Green＇s function approach under the adiabatic approximation. In the remaining two opposite terminals of the four-terminal structure, the quantum pump effect can produce an electric current whose magnitude and direction depends on the Fermi energy. The pumped currents are ascribed to the asymmetry of transmission coefficients with respect to the Fermi energy.
基金This project was supported by the Na- tional Natural Science Foundation of China （Grant No. 11004063） and the Fundamental Research Funds for the Central Universities, SCUT （Grant No. 2012ZZ0076）.
文摘Based on the scattering matrix approach.we systematically investigate the anharmonic effect of the pumped current in double-barrier strructures with adiabatic time-modulation of two sinusoidal AC driven potential heights. The pumped currem as a functionof the pha.se difference bet ween the two driven potentials looks like to be sinusoidal, but actually it contains sine functions of double and more phase difference, it is found that this kind of anharmonic effect of the pumped current is determined combinedly by the Berry curvature and parameter va.riation loop trajectory. Therefore small ratio of the driving amplitude and the static amplitude is not necessary for harmonic pattern in the pmnped era＇rent, to dominate for smooth Berry curvatureon the surface within the parameter variation loop.
