Based on the density functional theory, we calculate the band structure of an armchair carbon nanotube in an axial magnetic field. The result shows that there are two kinds of magnetic moments with different symmetrie...Based on the density functional theory, we calculate the band structure of an armchair carbon nanotube in an axial magnetic field. The result shows that there are two kinds of magnetic moments with different symmetries. One is the Aharonov-Bohm-type magnetic moment which can be easily understood with classical picture, the other belonging to the valence, and conduction sub-bands should be explained by quantum mechanics. We use an effective mass model to analyse the magnetic moments and by comparing with the result of first-principle calculation, we conclude that the effective mass model is reasonable to estimate the change of the band gap in magnetic fields.展开更多
Based on non-equilibrium Green＇s function theory and density functional theory, we investigate the vibrational property and electron-phonon （el-ph） interaction induced inelastic scattering in electron transport thr...Based on non-equilibrium Green＇s function theory and density functional theory, we investigate the vibrational property and electron-phonon （el-ph） interaction induced inelastic scattering in electron transport through metallic monoatomic wires.展开更多
Combining the non-equilibrium Green＇s function method and density functional theory, we provide a first-principle scheme to calculate the universal conductance fluctuation （UCF） in quasi one-dimensional monatomic c...Combining the non-equilibrium Green＇s function method and density functional theory, we provide a first-principle scheme to calculate the universal conductance fluctuation （UCF） in quasi one-dimensional monatomic chains subject to a magnetic field. Our results show that for these monatomic chains, the amplitude of the UCF is much smaller than the previous theoretical prediction for mesoscopic conductors by Lee et al. [Phys. Rev. Lett. 55 （1985） 1622; Phys. Rev. B 36 （1987） 1039] The reason is that the ergodic hypothesis fails in these nanowires due to the confinement of geometry. We ascribe the phenomenon to the flux-dependent density of states fluctuation.展开更多
The mesoscopic quantum interference phenomenon （QIP） can be observed and behaves as the oscillation of conductance in nano-devices when the external magnetic field changes. Excluding the factor of impurities or defe...The mesoscopic quantum interference phenomenon （QIP） can be observed and behaves as the oscillation of conductance in nano-devices when the external magnetic field changes. Excluding the factor of impurities or defects, specific QIP is determined by the sample geometry. We have improved a first-principles method based on the matrix Green＇s function and the density functional theory to simulate the transport behaviour of such systems under a magnetic field. We have studied two kinds of QIP： universal conductance fluctuation （UCF） and Aharonov Bohm effect （A-B effect）. We find that the amplitude of UCF is much smaller than the previous theoretical prediction. We have discussed the origin of difference and concluded that due to the failure of ergodic hypothesis, the ensemble statistics is not applicable, and the conductance fluctuation is determined by the flux-dependent density of states （DOSs）. We have also studied the relation between the UCF and the structure of sample. For a specific structure, an atomic circle, the A-B effect is observed and the origin of the oscillation is also discussed.展开更多
We study an ideal electron gas obeying fractional statistics.The parameters for exclusion statistics are given by the strength of the repulsive interactions.In some parameter regions,it is found the system shows itine...We study an ideal electron gas obeying fractional statistics.The parameters for exclusion statistics are given by the strength of the repulsive interactions.In some parameter regions,it is found the system shows itinerant ferromagnetism.展开更多
Using an all-atom-all-electron self-consistent LMTO band calculation and density functional theory method,we have studied the total energy of different NbCe systems.It appears that there is an unusual interface effect...Using an all-atom-all-electron self-consistent LMTO band calculation and density functional theory method,we have studied the total energy of different NbCe systems.It appears that there is an unusual interface effect on the energy,which predicts the possibility of artificial preparation for some NbCe superlattice systems.展开更多
文章评述了凝聚态物理从头计算(ab initio calculation)的一些最新进展.分8个问题进行了介绍,它们是:(1)静态密度泛函发展的两种思路;(2)固体的泛函:晶格常数的准确确定;(3)动态(含时)密度泛函及动态密度矩阵泛函;(4)半导体电子结构的计...文章评述了凝聚态物理从头计算(ab initio calculation)的一些最新进展.分8个问题进行了介绍,它们是:(1)静态密度泛函发展的两种思路;(2)固体的泛函:晶格常数的准确确定;(3)动态(含时)密度泛函及动态密度矩阵泛函;(4)半导体电子结构的计算:带隙和带序;(5)f电子和强关联金属;(6)莫特(Mott)绝缘体;(7)非共价(弱)相互作用;(8)以波函数为基础的研究.此外,文章还提供了一些相关的背景知识.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 90207009, 90206048 and 90406014.
文摘Based on the density functional theory, we calculate the band structure of an armchair carbon nanotube in an axial magnetic field. The result shows that there are two kinds of magnetic moments with different symmetries. One is the Aharonov-Bohm-type magnetic moment which can be easily understood with classical picture, the other belonging to the valence, and conduction sub-bands should be explained by quantum mechanics. We use an effective mass model to analyse the magnetic moments and by comparing with the result of first-principle calculation, we conclude that the effective mass model is reasonable to estimate the change of the band gap in magnetic fields.
基金Supported by the National Science Foundation of China under Grant Nos 90207009, 90206048, 90406014, 60440420450.
文摘Based on non-equilibrium Green＇s function theory and density functional theory, we investigate the vibrational property and electron-phonon （el-ph） interaction induced inelastic scattering in electron transport through metallic monoatomic wires.
基金Supported by the National Natural Science Foundation of China under Grant Nos 90207009, 90206048 and 90406014.
文摘Combining the non-equilibrium Green＇s function method and density functional theory, we provide a first-principle scheme to calculate the universal conductance fluctuation （UCF） in quasi one-dimensional monatomic chains subject to a magnetic field. Our results show that for these monatomic chains, the amplitude of the UCF is much smaller than the previous theoretical prediction for mesoscopic conductors by Lee et al. [Phys. Rev. Lett. 55 （1985） 1622; Phys. Rev. B 36 （1987） 1039] The reason is that the ergodic hypothesis fails in these nanowires due to the confinement of geometry. We ascribe the phenomenon to the flux-dependent density of states fluctuation.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 90207009, 90206048 and 90406014)
文摘The mesoscopic quantum interference phenomenon （QIP） can be observed and behaves as the oscillation of conductance in nano-devices when the external magnetic field changes. Excluding the factor of impurities or defects, specific QIP is determined by the sample geometry. We have improved a first-principles method based on the matrix Green＇s function and the density functional theory to simulate the transport behaviour of such systems under a magnetic field. We have studied two kinds of QIP： universal conductance fluctuation （UCF） and Aharonov Bohm effect （A-B effect）. We find that the amplitude of UCF is much smaller than the previous theoretical prediction. We have discussed the origin of difference and concluded that due to the failure of ergodic hypothesis, the ensemble statistics is not applicable, and the conductance fluctuation is determined by the flux-dependent density of states （DOSs）. We have also studied the relation between the UCF and the structure of sample. For a specific structure, an atomic circle, the A-B effect is observed and the origin of the oscillation is also discussed.
文摘We study an ideal electron gas obeying fractional statistics.The parameters for exclusion statistics are given by the strength of the repulsive interactions.In some parameter regions,it is found the system shows itinerant ferromagnetism.
文摘Using an all-atom-all-electron self-consistent LMTO band calculation and density functional theory method,we have studied the total energy of different NbCe systems.It appears that there is an unusual interface effect on the energy,which predicts the possibility of artificial preparation for some NbCe superlattice systems.
文摘文章评述了凝聚态物理从头计算(ab initio calculation)的一些最新进展.分8个问题进行了介绍,它们是:(1)静态密度泛函发展的两种思路;(2)固体的泛函:晶格常数的准确确定;(3)动态(含时)密度泛函及动态密度矩阵泛函;(4)半导体电子结构的计算:带隙和带序;(5)f电子和强关联金属;(6)莫特(Mott)绝缘体;(7)非共价(弱)相互作用;(8)以波函数为基础的研究.此外,文章还提供了一些相关的背景知识.
