We study the transmission dynamics of a driven two-level system dissipated by the two leads.Using nonequilibrium Green function,we derive an analytical transmission formula for an electron incident from the left lead,...We study the transmission dynamics of a driven two-level system dissipated by the two leads.Using nonequilibrium Green function,we derive an analytical transmission formula for an electron incident from the left lead,through the double quantum dots,to the right lead.Landauer-type conductance and current are also given.A discussion of the internal tunneling dynamics reveals crucial effects of the localization and delocalization on the transport of the system.展开更多
We show how the two interacting electrons in a field-driven coupled quantum dot can be used to prepare maximally entangled Bell states. The time durations of the oscillatory electric field for producing and maintainin...We show how the two interacting electrons in a field-driven coupled quantum dot can be used to prepare maximally entangled Bell states. The time durations of the oscillatory electric field for producing and maintaining such highly entangled states are identified by both analytic and exact numerical solutions of the quantum dynamical equations.展开更多
We investigate the dynamical processes taking place in nanodevices by high-frequency dc-ac fields.We found that Rabi oscillations between minibands are clearly identified under theoretical resonant conditions derived ...We investigate the dynamical processes taking place in nanodevices by high-frequency dc-ac fields.We found that Rabi oscillations between minibands are clearly identified under theoretical resonant conditions derived by an ideal two bands superlattice model,the resonant conditions have broadened,and the amount of broadening is about four times of the Rabi oscillation frequency.We also want to elucidate the role of different mechanisms that could lead to loss of quantum coherence.Our results show how the dephasing effects of disorder of interface roughness and doping fluctuation that destroy after some periods coherent oscillations,such as Rabi oscillations,can be reduced dramatically if we apply a bias static electric field to the superlattice system.Doping fluctuation's dephasing effect is much stronger than that of interface roughness in coherent process of realistic superlattices.展开更多
We calculated the vibrational free energies of the selected ordered compounds in the Ag-Cu system by using two kinds of methods: (1) calculating the phonon dispersion and density of states and the consequently vibrati...We calculated the vibrational free energies of the selected ordered compounds in the Ag-Cu system by using two kinds of methods: (1) calculating the phonon dispersion and density of states and the consequently vibrational free energies by using the method of ab initio inverted interatomic potentials and dynamic matrix;(2) the vibrational free energies determined by a Debye-Griineisen approximation. The Ag-Cu phase diagram is calculated by the cluster variation method. The results show that the solubility at Ag-rich end of the calculated phase diagram considering vibrational modes by using the first method is in better agreement with the experimental.展开更多
We study the dynamics of two-level systems under the influence of time-dependent external fields. An oscillation period describing the transition between two states is obtained analytically by the use of perturbation ...We study the dynamics of two-level systems under the influence of time-dependent external fields. An oscillation period describing the transition between two states is obtained analytically by the use of perturbation theory, from which the results for any special case can be derived. We illustrate two examples to show the advantage of our theory, in which the phenomenon of localization/delocalization can be addressed uniformly by oscillation period.展开更多
Based on a two-band tight-binding model,the dynamics of electrons under the action of static electric fields with Markoffian dephasing is investigated.The effective scattering time is obtained under the conditions of ...Based on a two-band tight-binding model,the dynamics of electrons under the action of static electric fields with Markoffian dephasing is investigated.The effective scattering time is obtained under the conditions of long-time limit and small interband communication through a perturbative calculation,from which the signature of Zener resonances and relatively long time evolution behavior are predicted.展开更多
Exact soliton solutions describing nonlinear dynamical behavior of Bloch electrons under action of dc-ac electric fields are obtained,from which it is found that the evolution behavior of Bloch electrons is always osc...Exact soliton solutions describing nonlinear dynamical behavior of Bloch electrons under action of dc-ac electric fields are obtained,from which it is found that the evolution behavior of Bloch electrons is always oscillatory in time,with oscillatory frequencies depending on electric fields.A number of phenomena associated with the translational symmetry of the system,the staggered localized states,as well as the relationship between intrinsic localized states and solitons are addressed.The corresponding energy,momentum,and norm are also studied.展开更多
基金Supported in part by the National Natural Science Foundation of China under Grant No.19725417the China Academy of Engineering Physics.
文摘We study the transmission dynamics of a driven two-level system dissipated by the two leads.Using nonequilibrium Green function,we derive an analytical transmission formula for an electron incident from the left lead,through the double quantum dots,to the right lead.Landauer-type conductance and current are also given.A discussion of the internal tunneling dynamics reveals crucial effects of the localization and delocalization on the transport of the system.
基金Supported in part by the National Natural Science Foundation of China under Grant No.19725417the China Academy of Engineering Physics.
文摘We show how the two interacting electrons in a field-driven coupled quantum dot can be used to prepare maximally entangled Bell states. The time durations of the oscillatory electric field for producing and maintaining such highly entangled states are identified by both analytic and exact numerical solutions of the quantum dynamical equations.
基金Supported in part by the National Natural Science Foundation of China under Grant No.19725417the National Climbing Project under Grant No.95-YU-41the China Academy of Engineering Physics.
文摘We investigate the dynamical processes taking place in nanodevices by high-frequency dc-ac fields.We found that Rabi oscillations between minibands are clearly identified under theoretical resonant conditions derived by an ideal two bands superlattice model,the resonant conditions have broadened,and the amount of broadening is about four times of the Rabi oscillation frequency.We also want to elucidate the role of different mechanisms that could lead to loss of quantum coherence.Our results show how the dephasing effects of disorder of interface roughness and doping fluctuation that destroy after some periods coherent oscillations,such as Rabi oscillations,can be reduced dramatically if we apply a bias static electric field to the superlattice system.Doping fluctuation's dephasing effect is much stronger than that of interface roughness in coherent process of realistic superlattices.
基金Supported in part by the National Natural Science Foundation of China under Grant No.19725417and the National PANDENG Project under Grant No.95-YU-41.
文摘We calculated the vibrational free energies of the selected ordered compounds in the Ag-Cu system by using two kinds of methods: (1) calculating the phonon dispersion and density of states and the consequently vibrational free energies by using the method of ab initio inverted interatomic potentials and dynamic matrix;(2) the vibrational free energies determined by a Debye-Griineisen approximation. The Ag-Cu phase diagram is calculated by the cluster variation method. The results show that the solubility at Ag-rich end of the calculated phase diagram considering vibrational modes by using the first method is in better agreement with the experimental.
基金the National Natural Science Foundation of China under Grant No.19725417the National Climbing Project of China,and a grant of the China Academy of Engineering and Physics.
文摘We study the dynamics of two-level systems under the influence of time-dependent external fields. An oscillation period describing the transition between two states is obtained analytically by the use of perturbation theory, from which the results for any special case can be derived. We illustrate two examples to show the advantage of our theory, in which the phenomenon of localization/delocalization can be addressed uniformly by oscillation period.
基金Supported in part by the National Natural Science Foundation of China under Grant No.19725417the Grant of China Academy of Engineering and Physics。
文摘Based on a two-band tight-binding model,the dynamics of electrons under the action of static electric fields with Markoffian dephasing is investigated.The effective scattering time is obtained under the conditions of long-time limit and small interband communication through a perturbative calculation,from which the signature of Zener resonances and relatively long time evolution behavior are predicted.
基金Supported in part by the National Natural Science Foundation of China under Grant Nos.19674059,19674063 and 19677101.
文摘Exact soliton solutions describing nonlinear dynamical behavior of Bloch electrons under action of dc-ac electric fields are obtained,from which it is found that the evolution behavior of Bloch electrons is always oscillatory in time,with oscillatory frequencies depending on electric fields.A number of phenomena associated with the translational symmetry of the system,the staggered localized states,as well as the relationship between intrinsic localized states and solitons are addressed.The corresponding energy,momentum,and norm are also studied.
