Transport properties are theoretically studied through an anisotropy single-molecule magnet symmetrically connected to two identical ferromagnetic leads. It is found that even though in parallel configuration of leads...Transport properties are theoretically studied through an anisotropy single-molecule magnet symmetrically connected to two identical ferromagnetic leads. It is found that even though in parallel configuration of leads’ magnetizations, the total current still greatly depends on the spin polarization of leads at certain particular bias region, and thus for large polarization a prominent negative differential conductance （NDC） emerges. This originates from the joint effect of single-direction transitions and spin polarization, which removes the symmetry between spin-up and spin-down transitions. The present mechanism of NDC is remarkably different from the previously reported mechanisms. To clarify the physics of the NDC, we further monitored the shot noise spectroscopy and found that the appearance of the NDC is accompanied by the rapid decrease of Fano factor.展开更多
The electronic transport properties of a single thiolated arylethynylene molecule with 9,10-dihydroanthracene core, denoted as TADHA, is studied by using non-equilibrium Green＇s function formalism combined with ab in...The electronic transport properties of a single thiolated arylethynylene molecule with 9,10-dihydroanthracene core, denoted as TADHA, is studied by using non-equilibrium Green＇s function formalism combined with ab initio calculations. The numerical results show that the TADHA molecule exhibits excellent negative differential conductance （NDC） behavior at lower bias regime as probed experimentally. The NDC behavior of TADHA molecule originates from the Stark effect of the applied bias voltage, by which the highest occupied molecular orbital （HOMO） and the HOMO-1 are pulled apart and become localized. The NDC behavior of TADHA molecular system is tunable by changing the electrode distance. Shortening the electrode separation can enhance the NDC effect which is attributed to the possible increase of coupling between the two branches of TADHA molecule.展开更多
The effect of the negative differential conductance of a ferromagnetic barrier on the surface of a topological insulat（ is theoretically investigated. Due to the changes of the shape and position of the Fermi surface...The effect of the negative differential conductance of a ferromagnetic barrier on the surface of a topological insulat（ is theoretically investigated. Due to the changes of the shape and position of the Fermi surfaces in the ferromagnetic barrie the transport processes can be divided into three kinds： the total, partial, and blockade transmission mechanisms. The bias voltage can give rise to the transition of the transport processes from partial to blockade transmission mechanisms, which results in a considerable effect of negative differential conductance. With appropriate structural parameters, the currenl voltage characteristics show that the minimum value of the current can reach to zero in a wide range of the bias voltag and then a large peak-to-valley current ratio can be obtained.展开更多
A simulation model and the dynamics of the forced modulation doped heterostructure, which operates in the state far from thermodynamic equilibrium, are discussed. The numerical simulations clearly reveal that the sys...A simulation model and the dynamics of the forced modulation doped heterostructure, which operates in the state far from thermodynamic equilibrium, are discussed. The numerical simulations clearly reveal that the system under an appropriate bias including DC and AC voltages exhibits expected complex dynamical behaviors. The amplitude and frequency of the externally applied microwave field are taken as the control parameters in the system. Because many nonlinear dynamical systems may have more than one possible time asympotic final state depending on the different initial conditions, the basins of attractions of both ordinary attractor and chaotic attractor are also studied respecively. Finally, as a possible application a method based on pulse driving to control chaos in semiconductor is proposed.展开更多
The superheterodyne amplification of electromagnetic waves is investigated when the resonant three-wave interaction of two electromagnetic waves with the space charge wave occurs in the waveguides nitride <em>n&...The superheterodyne amplification of electromagnetic waves is investigated when the resonant three-wave interaction of two electromagnetic waves with the space charge wave occurs in the waveguides nitride <em>n</em>-GaN, <em>n</em>-InN films-dielectric. The amplification of SCW waves due to the negative differential conductivity is investigated in nitride <em>n</em>-GaN, <em>n</em>-InN films at the frequencies <em>f</em> ≤ 400 GHz in the lower part of the terahertz (THz) range. The electromagnetic waves are either in the upper part of THz range or in the optical range. The superheterodyne amplification is considered in two geometries, the collinear one in which the three interacting waves travel in the same direction and the anti-collinear geometry where the second electromagnetic wave propagates in the opposite direction. The preferences and drawbacks of each geometry are pointed out. The finite width of space charge waves leads to decrease of increments of amplification.展开更多
We have investigated the transport properties of the Dirac fermions through a ferromagnetic barrier junction on the surface of a strong topologicM insulator. The current-voltage characteristic curve and the tunneling ...We have investigated the transport properties of the Dirac fermions through a ferromagnetic barrier junction on the surface of a strong topologicM insulator. The current-voltage characteristic curve and the tunneling conductance are calculated theoretically. Two interesting transport features are predicted： observable negative differential conductances and linear conductances tunable from unit to nearly zero. These features can be magnetically manipulated simply by changing the spacial orientation of the magnetization. Our results may contribute to the development of high-speed switching and functional applications or electricalIy controlled magnetization switching.展开更多
Electronic transport through a vibrating double quantum dot （DQD） in contact with noncollinear ferromagnetic （FM） leads is investigated. The state transition between the two dots of the DQD is excited by an AC mic...Electronic transport through a vibrating double quantum dot （DQD） in contact with noncollinear ferromagnetic （FM） leads is investigated. The state transition between the two dots of the DQD is excited by an AC microwave driving field. The corresponding currents and differential conductance are calculated in the Coulomb blockade regime by means of the Born-Markov master equation. It is shown that the interplay between electrons and phonons gives rise to phonon-assisted tunneling resonances and Franck-Condon blockade under certain conditions. In noncollinear magnetic configurations, spin-blockade effects are also observed, and the angle of polarization has some influence on the transport characteristics.展开更多
The single thiolated arylethynylene molecule with 9,10-dihydroanthracene core（denoted as TADHA） possesses pronounced negative differential conductance（NDC） behavior at lower bias regime. The adsorption effects of ...The single thiolated arylethynylene molecule with 9,10-dihydroanthracene core（denoted as TADHA） possesses pronounced negative differential conductance（NDC） behavior at lower bias regime. The adsorption effects of F2 molecule on the current and NDC behavior of TADHA molecular junctions are studied by applying non-equilibrium Green＇s formalism combined with density functional theory. The numerical results show that the F2 molecule adsorbed on the benzene ring of TADHA molecule near the electrode can dramatically suppresses the current of TADHA molecular junction. When the F2 molecule adsorbed on the conjugated segment of 9,10-dihydroanthracene core of TADHA molecule, an obviously asymmetric effect on the current curves induces the molecular system showing apparent rectifier behavior. However, the current especially the NDC behavior have been significantly enlarged when F2 addition reacted with triple bond of TADHA molecule.展开更多
We study dynamics of the forced modulation-doped GaAs/AIGaAs heterostructure de-vices . The coupled differential equations governing the dynamical behaviors are numerically simulated. Biased with an appropriate dc fie...We study dynamics of the forced modulation-doped GaAs/AIGaAs heterostructure de-vices . The coupled differential equations governing the dynamical behaviors are numerically simulated. Biased with an appropriate dc field, the system exhibits two states: spontaneous current oscillation and fixed points. By imposing an ac driving force, the dynamical system shows frequency locking, quasiperiodicity, and chaos, which are sensitive to the amplitude and frequency of the externally ap-plied periodical microwave field. The basins of attraction of both ordinary attractors and strange attrac-tors are presented.展开更多
基金Project supported by the Program for New Century Excellent Talents in University of China (Grant No. NCET-10-0090)the National Natural Science Foundation of China (Grant Nos. 10974058, 11174088, and 11274124)the Natural Science Foundation of Guangdong Province of China (Grant No. S2012010010681)
文摘Transport properties are theoretically studied through an anisotropy single-molecule magnet symmetrically connected to two identical ferromagnetic leads. It is found that even though in parallel configuration of leads’ magnetizations, the total current still greatly depends on the spin polarization of leads at certain particular bias region, and thus for large polarization a prominent negative differential conductance （NDC） emerges. This originates from the joint effect of single-direction transitions and spin polarization, which removes the symmetry between spin-up and spin-down transitions. The present mechanism of NDC is remarkably different from the previously reported mechanisms. To clarify the physics of the NDC, we further monitored the shot noise spectroscopy and found that the appearance of the NDC is accompanied by the rapid decrease of Fano factor.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11374195 and 11405098)the Natural Science Foundation of Shandong Province,China(Grant No.ZR2013FM006)
文摘The electronic transport properties of a single thiolated arylethynylene molecule with 9,10-dihydroanthracene core, denoted as TADHA, is studied by using non-equilibrium Green＇s function formalism combined with ab initio calculations. The numerical results show that the TADHA molecule exhibits excellent negative differential conductance （NDC） behavior at lower bias regime as probed experimentally. The NDC behavior of TADHA molecule originates from the Stark effect of the applied bias voltage, by which the highest occupied molecular orbital （HOMO） and the HOMO-1 are pulled apart and become localized. The NDC behavior of TADHA molecular system is tunable by changing the electrode distance. Shortening the electrode separation can enhance the NDC effect which is attributed to the possible increase of coupling between the two branches of TADHA molecule.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11104059 and 61176089)
文摘The effect of the negative differential conductance of a ferromagnetic barrier on the surface of a topological insulat（ is theoretically investigated. Due to the changes of the shape and position of the Fermi surfaces in the ferromagnetic barrie the transport processes can be divided into three kinds： the total, partial, and blockade transmission mechanisms. The bias voltage can give rise to the transition of the transport processes from partial to blockade transmission mechanisms, which results in a considerable effect of negative differential conductance. With appropriate structural parameters, the currenl voltage characteristics show that the minimum value of the current can reach to zero in a wide range of the bias voltag and then a large peak-to-valley current ratio can be obtained.
文摘A simulation model and the dynamics of the forced modulation doped heterostructure, which operates in the state far from thermodynamic equilibrium, are discussed. The numerical simulations clearly reveal that the system under an appropriate bias including DC and AC voltages exhibits expected complex dynamical behaviors. The amplitude and frequency of the externally applied microwave field are taken as the control parameters in the system. Because many nonlinear dynamical systems may have more than one possible time asympotic final state depending on the different initial conditions, the basins of attractions of both ordinary attractor and chaotic attractor are also studied respecively. Finally, as a possible application a method based on pulse driving to control chaos in semiconductor is proposed.
文摘The superheterodyne amplification of electromagnetic waves is investigated when the resonant three-wave interaction of two electromagnetic waves with the space charge wave occurs in the waveguides nitride <em>n</em>-GaN, <em>n</em>-InN films-dielectric. The amplification of SCW waves due to the negative differential conductivity is investigated in nitride <em>n</em>-GaN, <em>n</em>-InN films at the frequencies <em>f</em> ≤ 400 GHz in the lower part of the terahertz (THz) range. The electromagnetic waves are either in the upper part of THz range or in the optical range. The superheterodyne amplification is considered in two geometries, the collinear one in which the three interacting waves travel in the same direction and the anti-collinear geometry where the second electromagnetic wave propagates in the opposite direction. The preferences and drawbacks of each geometry are pointed out. The finite width of space charge waves leads to decrease of increments of amplification.
基金Supported by National Natural Science Foundation of China under Grant Nos.11174088,11175067,11274124
文摘We have investigated the transport properties of the Dirac fermions through a ferromagnetic barrier junction on the surface of a strong topologicM insulator. The current-voltage characteristic curve and the tunneling conductance are calculated theoretically. Two interesting transport features are predicted： observable negative differential conductances and linear conductances tunable from unit to nearly zero. These features can be magnetically manipulated simply by changing the spacial orientation of the magnetization. Our results may contribute to the development of high-speed switching and functional applications or electricalIy controlled magnetization switching.
基金Project supported by the National Natural Science Foundation of China(Grant No.61275059)
文摘Electronic transport through a vibrating double quantum dot （DQD） in contact with noncollinear ferromagnetic （FM） leads is investigated. The state transition between the two dots of the DQD is excited by an AC microwave driving field. The corresponding currents and differential conductance are calculated in the Coulomb blockade regime by means of the Born-Markov master equation. It is shown that the interplay between electrons and phonons gives rise to phonon-assisted tunneling resonances and Franck-Condon blockade under certain conditions. In noncollinear magnetic configurations, spin-blockade effects are also observed, and the angle of polarization has some influence on the transport characteristics.
基金Project supported by the National Natural Science Foundation of China(Grant No.11374195)the Taishan Scholar Project of Shandong Province,Chinathe Jinan Youth Science and Technology Star Project,China(Grant No.201406004)
文摘The single thiolated arylethynylene molecule with 9,10-dihydroanthracene core（denoted as TADHA） possesses pronounced negative differential conductance（NDC） behavior at lower bias regime. The adsorption effects of F2 molecule on the current and NDC behavior of TADHA molecular junctions are studied by applying non-equilibrium Green＇s formalism combined with density functional theory. The numerical results show that the F2 molecule adsorbed on the benzene ring of TADHA molecule near the electrode can dramatically suppresses the current of TADHA molecular junction. When the F2 molecule adsorbed on the conjugated segment of 9,10-dihydroanthracene core of TADHA molecule, an obviously asymmetric effect on the current curves induces the molecular system showing apparent rectifier behavior. However, the current especially the NDC behavior have been significantly enlarged when F2 addition reacted with triple bond of TADHA molecule.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 69871016).
文摘We study dynamics of the forced modulation-doped GaAs/AIGaAs heterostructure de-vices . The coupled differential equations governing the dynamical behaviors are numerically simulated. Biased with an appropriate dc field, the system exhibits two states: spontaneous current oscillation and fixed points. By imposing an ac driving force, the dynamical system shows frequency locking, quasiperiodicity, and chaos, which are sensitive to the amplitude and frequency of the externally ap-plied periodical microwave field. The basins of attraction of both ordinary attractors and strange attrac-tors are presented.
