We study persistent currents in the double Aharonov-Bohm ring connected to two electron reservoirs by quantum waveguide theory. It is found that the persistent currents in the double Aharonov-Bohm ring depend .on the ...We study persistent currents in the double Aharonov-Bohm ring connected to two electron reservoirs by quantum waveguide theory. It is found that the persistent currents in the double Aharonov-Bohm ring depend .on the direction of the current flow from one reservoir to another. When the direction of the current flow reverses, tl2e persistent current in each ring of the double Aharonov-Bohm ring changes. If the two rings are of the same size, the persistent currents in the left and the right rings exchange at the reversal of the current flow direction.展开更多
Taking into account both the intrinsic curvature and Zeeman effects, persistent currents in a multi-walled carbon nanotorus are explored by using a supercell method, within the tight-binding formalism. It is shown tha...Taking into account both the intrinsic curvature and Zeeman effects, persistent currents in a multi-walled carbon nanotorus are explored by using a supercell method, within the tight-binding formalism. It is shown that in the absence of the Zeeman effect, the intrinsic curvature induces some dramatic changes in energy spectra and thus changes in the shape of the flux-dependent current. A paramagnetism diamagnetism transition is observed. With consideration of the Zeeman splitting energy, the period of persistent current is destroyed, and a diamagnetism-paramagnetism transition is obtained at high magnetic field. In addition, we further explore the effect of external electric field energy （Eef） on persistent current, indicating that it changes unmonotonously with Eef.展开更多
We theoretically study the persistent currents flowing in a Rashba quantum ring subjected to the Rashba spinorbit interaction. By introducing uniform or nonuniform magnetization into the ring, we find that a nonzero p...We theoretically study the persistent currents flowing in a Rashba quantum ring subjected to the Rashba spinorbit interaction. By introducing uniform or nonuniform magnetization into the ring, we find that a nonzero persistent charge current circulates in the ring, which stems from the original equilibrium spin current due to the Rashba spinorbit interaction. Because of broken time reversal symmetry, the two oppositely flowing spin-up and spin-down charge currents of the equilibrium spin current are no longer equal, and so a net persistent charge current can flow in the system. It is also found that the persistent current can be modulated by the Fermi energy, the Rashba spin-orbit interaction strength and the magnetization in the ring. Moreover, the magnetization perpendicular to the ring plane can optimize the current. The persistent current flowing in the ring is a manifestation of the nonzero equilibrium spin current existing in the ring.展开更多
By making the analogy between the operator Hamiltonians of a mesoscopic ring carrying the persistent current and a Josephson junction we have introduced a phase operator and entangled state representation to establish...By making the analogy between the operator Hamiltonians of a mesoscopic ring carrying the persistent current and a Josephson junction we have introduced a phase operator and entangled state representation to establish a theoretical formalism for the ring system.展开更多
The persistent current and transmission of two connected Aharonov-Bohm rings coupled to external leads are solved analytically. The conditions on which we may observe persistent current, zero or perfect transmission a...The persistent current and transmission of two connected Aharonov-Bohm rings coupled to external leads are solved analytically. The conditions on which we may observe persistent current, zero or perfect transmission as well as Fano resonance are studied.展开更多
The effect ofthe edge state on the persistent current in quasi-1D mesoscopic rings with a screened interactionwhich exists only between nearest-neighboring particles is studied with the Hartree-Fock approximation. The...The effect ofthe edge state on the persistent current in quasi-1D mesoscopic rings with a screened interactionwhich exists only between nearest-neighboring particles is studied with the Hartree-Fock approximation. The theoreticalvalue of the current magnitude is greatly enhanced by both the edge state and the Coulomb interaction, and pinningthe electrons into a lattice is good for the enhancement if screening happens. In high dimensional systems the screeningeffect can make the interacting range show anisotropy, and create a tendency of gathering for particles with a repulsivepotential.展开更多
The persistent current in three-dimensional （P × N2） nanorings as a function of the unit cell number （P）, the channel number （M =N2）, surface disorder （ζ）, and temperature （T） is theoretically investig...The persistent current in three-dimensional （P × N2） nanorings as a function of the unit cell number （P）, the channel number （M =N2）, surface disorder （ζ）, and temperature （T） is theoretically investigated in terms of rotational symmetry. On the whole, the typical current increases linearly with √M but decreases exponentially with P, while wide fluctuations exist therein. In the presence of surface disorder, the persistent current decreases with ζ in the regime of weak disorder but increases in the regime of strong disorder. In addition, it is found that the persistent current in perfect rings decreases exponentially with temperature even at T 〈 T＊, while in most disorder rings, the typical current decreases slightly with temperature at T 〈 T＊.展开更多
A new non-perturbative method is used to discuss the persistent current in a one-dimensional mesoscopic ring threaded by a flux φ with electron-phonon interaction in the lattice model. The current is periodic in φ w...A new non-perturbative method is used to discuss the persistent current in a one-dimensional mesoscopic ring threaded by a flux φ with electron-phonon interaction in the lattice model. The current is periodic in φ with a flux quantum φ 0 and the electron-phonon interaction suppresses the persistent current. By considering the contributions of many-phonon correlations, we could obtain more accurate results.展开更多
We present a comprehensive view and details of calculations on Aharonov-Anandan phase for the charged particles in the external electric and magnetic fields for a nonadiabatic process.We derive,with consideration of a...We present a comprehensive view and details of calculations on Aharonov-Anandan phase for the charged particles in the external electric and magnetic fields for a nonadiabatic process.We derive,with consideration of a spin-orbit interaction and Zeemann Splitting,the persistent currents as a response to an Aharonov-Casher topological interference effect in one-dimensional mesoscopic ring.We also establish a connection to Berry adiabatic phase with deduced dynamical-nature dependence in the nonadiabatic process.The second quantization representation has also been employed in exhibition of persistent currents in the many-body case.展开更多
In this work,for the first time in the relevant literature,the persistent currents(PC)and induced magnetic fields(IMF)of an endofullerene molecule entrapping a hydrogen atom,under spherical confinement,are investigate...In this work,for the first time in the relevant literature,the persistent currents(PC)and induced magnetic fields(IMF)of an endofullerene molecule entrapping a hydrogen atom,under spherical confinement,are investigated.The endofullerene molecule is enclosed within a spherical region and embedded in a plasma environment.The plasma environment is depicted with the more general exponential cosine screened Coulomb potential,and its relevant effects are analyzed by considering plasma screening parameters.The relevant model for endohedral confinement is the Woods-Saxon confinement potential,which is compatible with experimental data.The effects of various forms of Cn are thoroughly elucidated via the analysis of the confinement depth,spherical shell thickness,the inner radius,and the smoothing parameters.To find the bound states in the spherically confined endofullerene,the decoupling of the second-order Dirac equation for the large and small components of the radial atomic wave functions is considered.The Dirac equation with the interaction potential is solved numerically by using the Runge-Kutta-Fehlberg method via the decoupling formalism.The influence of spin orientations on the PC and IMF is also elucidated.The effects of spherical confinement,plasma shielding,and the structural properties of the fullerene on the PC and IMF are thoroughly viewed.Moreover,under given physical conditions,the optimal ranges of these effects are determined.展开更多
In this paper the macroscopic quantum state of Bose-Einstein condensates in optical lattices is studied by solving the periodic Gross-Pitaevskii equation in one-dimensional geometry. It is shown that an exact solution...In this paper the macroscopic quantum state of Bose-Einstein condensates in optical lattices is studied by solving the periodic Gross-Pitaevskii equation in one-dimensional geometry. It is shown that an exact solution seen to be a travelling wave of excited macroscopic quantum states resultes in a persistent atom current, which can be controlled by adjusting of the barrier height of the optical periodic potential. A critical condition to generate the travelling wave is demonstrated and we moreover propose a practical experiment to realize the persistent atom current in a toroidal atom waveguide.展开更多
Objective ：To investigate the different suppressive effect of lidocaine on persistent Na^＋ current and transient Na^＋ current in injured or uninjured dorsal root ganglion neurons. Methods： Totally 23 SD rats were ...Objective ：To investigate the different suppressive effect of lidocaine on persistent Na^＋ current and transient Na^＋ current in injured or uninjured dorsal root ganglion neurons. Methods： Totally 23 SD rats were randomly divided into 2 groups： control group （n： 10） and chronically compressed DRG （dorsal root ganglion） group （CCD group, n= 13）. Rats were anesthetized and DRG was isolated. Single DRG neuron was isolated by enzymatic disassociation method. Persistent Na^＋ current （INap） and transient Na^＋ current （INaT） were elicited in voltage clamp mode. Results： The presence of INap was testified in most DRG neurons （38/46 neurons in CCD group and 31/39 neurons in control group, P〉0. 05）. However, the cur- rent density of INap in CCD group （4. 6±0. 6 pA/pF, n=38 neurons） was greater than that in control group （2.5±0.4 pA/pF, n=31 neurons） （P〈0. 05）. The characteristics of INap was observed and found that INap could he blocked by 0.2 μmol/L tetrodotoxin easily. Furthermore, the does-effect relationship of lidocaine on INaP and IN.T were also examined. INaP and IN.T were suppressed by different concentrations of li- docaine, the range for INap was 5-20 μmol/L and for INaT was 0. 05-2 mmol/L. Conclusion： INap and INaT were suppressed by different concentrations of lidocaine. INap was suppressed by very low concentration of lidocaine （5-20 μmol/L）. However, INaT could only be blocked by high concentration of lidocaine （0.05-2 mmol/L）.展开更多
The aim of this study was to investigate the effect of hypoxia on the sodium current of rat cardiomyocytes in order to explore ion channel mechanism of cardiomyocyte hypoxia.The rat cardiomyocytes were isolated by acu...The aim of this study was to investigate the effect of hypoxia on the sodium current of rat cardiomyocytes in order to explore ion channel mechanism of cardiomyocyte hypoxia.The rat cardiomyocytes were isolated by acute enzymatic hydrolysis.A group of untreated cells were used to record sodium currents using whole-cell patch-clamp technique,another group was subjected to hypoxia and record sodium currents using same technique.The results showed that the morphological trajectory of sodium hypoxia was not changed compared with that of normal cells.The I-V curve of hypoxic cells was significantly higher than that of normal cells,and the peak current of INa was 15.68%higher than that of normal cells(P<0.0001).Activation potential of normal and hypoxia cells was about-40mV,the maximum peak current corresponds to the stimulation voltage of-25mV.The above results suggest that rat cardiomyocytes sodium current increases in the case of hypoxia.展开更多
Using an equation of motion technique, we investigate the Kondo effect in a quantum dot coupled to ferromagnetic leads and a mesoscopic ring. It is shown that the Kondo resonance at the Fermi level of the dot presents...Using an equation of motion technique, we investigate the Kondo effect in a quantum dot coupled to ferromagnetic leads and a mesoscopic ring. It is shown that the Kondo resonance at the Fermi level of the dot presents the periodic change along with the aggrandizement of the magnetic flux and the number of lattice sites NR in the mesoscopic ring, and for the antiparallel spin alignment the Kondo resonances for spin-up and spin-down configurations appear at the same position. However, for the parallel spin alignment, the Kondo resonance splits for the spin-up and spin-down configurations.展开更多
We investigate the spin-flip process through double quantum dots coupled to two ferromagnetic leads in series. By means of the slave-boson mean-field approximation, we calculate the density of states in the Kondo regi...We investigate the spin-flip process through double quantum dots coupled to two ferromagnetic leads in series. By means of the slave-boson mean-field approximation, we calculate the density of states in the Kondo regime for two different configurations of the leads. It is found that transport shows some remarkable properties depending on the spin-flip strength. These effects may be useful in exploiting the role of electronic correlation in spintronics.展开更多
We derive an exact expression for the transmission coefficient through an Aharonov-Bohm ring with a side-coupled quantum dot using the scattering-matrix approach. We show a sudden AB phase change by π as the quantum ...We derive an exact expression for the transmission coefficient through an Aharonov-Bohm ring with a side-coupled quantum dot using the scattering-matrix approach. We show a sudden AB phase change by π as the quantum dot is tuned across the resonance. The Aharonow-Bohm oscillation amplitude can be modulated effectively by tuning the quantum dot level, The transmission coefficient has an expression of the generalized Fano form with a complex Fano parameter q in the presence of the Aharonov-Bohm flux.展开更多
We theoretically investigate the Kondo effect of a quantum dot embedded in a mesoscopic Aharonov-Bohm （AIR） ring in the presence of the spin flip processes by means of the one-impurity Anderson Hamiltonian. Based on...We theoretically investigate the Kondo effect of a quantum dot embedded in a mesoscopic Aharonov-Bohm （AIR） ring in the presence of the spin flip processes by means of the one-impurity Anderson Hamiltonian. Based on the slave-boson mean-field theory, we find that in this system the persistent current （PC） sensitively depends on the parity and size of the AB ring and can be tuned by the spin-flip scattering （R）. In the small AB ring, the PC is suppressed due to the enhancing R weakening the Kondo resonance. On the contrary, in the large AB ring, with R increasing, the peak of PC firstly moves up to max-peak and then down. Especially, the PC phase shift of π appears suddenly with the proper value of R, implying the existence of the anomalous Kondo effect in this system. Thus this system may be a carldidate for quantum switch.展开更多
We theoretically study the properties of the ground state of the parallel-coupled double quantum dots embedded in a mesoscopic ring in the Kondo regime by means of the two-impurity Anderson Hamiltonian. The Hamiltonia...We theoretically study the properties of the ground state of the parallel-coupled double quantum dots embedded in a mesoscopic ring in the Kondo regime by means of the two-impurity Anderson Hamiltonian. The Hamiltonian is solved by means of the slave-boson mean-field theory. We find that in this system, the persistent current depends sensitively on both the parity of this system and the size of the ring. In the strong coupling regime, the giant sharp current peak appears, at the same time, the parity dependence of the persistent current disappears. These imply that in the strong coupling regime, there exists giant Kondo resonance and the two dots can be coupled coherently. Thus this system might be a candidate for future device applications.展开更多
We theoretically investigate the properties of the ground state of the strongly correlated T-shaped double quantum dots embedded in an Aharonov-Bohm ring in the Kondo regime by means of the one-impurity Anderson Hamil...We theoretically investigate the properties of the ground state of the strongly correlated T-shaped double quantum dots embedded in an Aharonov-Bohm ring in the Kondo regime by means of the one-impurity Anderson Hamiltonian. It is found that in this system, the persistent current depends sensitively on the parity and size of the ring. With the increase of interdot coupling, the persistent current is suppressed due to the enhancing Fano interference weakening the Kondo effect. Moreover, when the spin of quantum dot embedded in the Aharonov- Bohm ring is screened, the persistent current peak is not affected by interdot coupling. Thus this model may be a new candidate for detecting Kondo screening cloud.展开更多
A model is proposed to study the quantum rings with two deeply bound electrons under a variable magnetic field. The emphasis is placed to clarify the effect of the size （diameter） and the width of the ring on the fr...A model is proposed to study the quantum rings with two deeply bound electrons under a variable magnetic field. The emphasis is placed to clarify the effect of the size （diameter） and the width of the ring on the fractional Aharonov-Bohm oscillation. It was found that the reduction of size will lead to a very strong oscillation in the ground state energy and in the persistent current. The electronic correlation has also been demonstrated by showing the nodal structures of wave functions.展开更多
基金The project supported by National Natural Science Foundation of China under Grant No. 10347004
文摘We study persistent currents in the double Aharonov-Bohm ring connected to two electron reservoirs by quantum waveguide theory. It is found that the persistent currents in the double Aharonov-Bohm ring depend .on the direction of the current flow from one reservoir to another. When the direction of the current flow reverses, tl2e persistent current in each ring of the double Aharonov-Bohm ring changes. If the two rings are of the same size, the persistent currents in the left and the right rings exchange at the reversal of the current flow direction.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10674113)Program for New Century Excellent Talents in University of China (Grant No. NCET-06-0707)+2 种基金Foundation for the Author of National Excellent Doctoral Dissertation of China (Grant No. 200726)Scientific Research Fund of Hunan Provincial Education Department of China (Grant No. 06A071)partially by Hunan Provincial Innovation Foundation For Postgraduate (Grant No. S2008yjscx06)
文摘Taking into account both the intrinsic curvature and Zeeman effects, persistent currents in a multi-walled carbon nanotorus are explored by using a supercell method, within the tight-binding formalism. It is shown that in the absence of the Zeeman effect, the intrinsic curvature induces some dramatic changes in energy spectra and thus changes in the shape of the flux-dependent current. A paramagnetism diamagnetism transition is observed. With consideration of the Zeeman splitting energy, the period of persistent current is destroyed, and a diamagnetism-paramagnetism transition is obtained at high magnetic field. In addition, we further explore the effect of external electric field energy （Eef） on persistent current, indicating that it changes unmonotonously with Eef.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 110704032 and 110704033)the Natural Science Foundation of Jiangsu Province of China (Grant No. BK2010416)the National Basic Research Development Program of China (Grant No. 2009CB945504)
文摘We theoretically study the persistent currents flowing in a Rashba quantum ring subjected to the Rashba spinorbit interaction. By introducing uniform or nonuniform magnetization into the ring, we find that a nonzero persistent charge current circulates in the ring, which stems from the original equilibrium spin current due to the Rashba spinorbit interaction. Because of broken time reversal symmetry, the two oppositely flowing spin-up and spin-down charge currents of the equilibrium spin current are no longer equal, and so a net persistent charge current can flow in the system. It is also found that the persistent current can be modulated by the Fermi energy, the Rashba spin-orbit interaction strength and the magnetization in the ring. Moreover, the magnetization perpendicular to the ring plane can optimize the current. The persistent current flowing in the ring is a manifestation of the nonzero equilibrium spin current existing in the ring.
基金The project supported by National Natural Science Foundation of China under Grant No. 10574060 and the Ph,D Tutoring Foundation of Educational Ministry of China
文摘By making the analogy between the operator Hamiltonians of a mesoscopic ring carrying the persistent current and a Josephson junction we have introduced a phase operator and entangled state representation to establish a theoretical formalism for the ring system.
文摘The persistent current and transmission of two connected Aharonov-Bohm rings coupled to external leads are solved analytically. The conditions on which we may observe persistent current, zero or perfect transmission as well as Fano resonance are studied.
文摘The effect ofthe edge state on the persistent current in quasi-1D mesoscopic rings with a screened interactionwhich exists only between nearest-neighboring particles is studied with the Hartree-Fock approximation. The theoreticalvalue of the current magnitude is greatly enhanced by both the edge state and the Coulomb interaction, and pinningthe electrons into a lattice is good for the enhancement if screening happens. In high dimensional systems the screeningeffect can make the interacting range show anisotropy, and create a tendency of gathering for particles with a repulsivepotential.
基金supported by the National Natural Science Foundation of China(Grant No i0674113)Program for New Century Excellent Talents in University of China(Grant No NCET-06-0707)+1 种基金Foundation for the Author of National Excellent Doctoral Dissertation of China(Grant No 200726)partially by Scientific Research Fund of Hunan Provincial Education Department of China (Grant No 06A071)
文摘The persistent current in three-dimensional （P × N2） nanorings as a function of the unit cell number （P）, the channel number （M =N2）, surface disorder （ζ）, and temperature （T） is theoretically investigated in terms of rotational symmetry. On the whole, the typical current increases linearly with √M but decreases exponentially with P, while wide fluctuations exist therein. In the presence of surface disorder, the persistent current decreases with ζ in the regime of weak disorder but increases in the regime of strong disorder. In addition, it is found that the persistent current in perfect rings decreases exponentially with temperature even at T 〈 T＊, while in most disorder rings, the typical current decreases slightly with temperature at T 〈 T＊.
文摘A new non-perturbative method is used to discuss the persistent current in a one-dimensional mesoscopic ring threaded by a flux φ with electron-phonon interaction in the lattice model. The current is periodic in φ with a flux quantum φ 0 and the electron-phonon interaction suppresses the persistent current. By considering the contributions of many-phonon correlations, we could obtain more accurate results.
基金The project supported by National Natural Science Foundation of China under Grant Nos.90103077 and 10274069Natural Science Foundation of Guangdong Province of China under Grant No.011151
文摘We present a comprehensive view and details of calculations on Aharonov-Anandan phase for the charged particles in the external electric and magnetic fields for a nonadiabatic process.We derive,with consideration of a spin-orbit interaction and Zeemann Splitting,the persistent currents as a response to an Aharonov-Casher topological interference effect in one-dimensional mesoscopic ring.We also establish a connection to Berry adiabatic phase with deduced dynamical-nature dependence in the nonadiabatic process.The second quantization representation has also been employed in exhibition of persistent currents in the many-body case.
文摘In this work,for the first time in the relevant literature,the persistent currents(PC)and induced magnetic fields(IMF)of an endofullerene molecule entrapping a hydrogen atom,under spherical confinement,are investigated.The endofullerene molecule is enclosed within a spherical region and embedded in a plasma environment.The plasma environment is depicted with the more general exponential cosine screened Coulomb potential,and its relevant effects are analyzed by considering plasma screening parameters.The relevant model for endohedral confinement is the Woods-Saxon confinement potential,which is compatible with experimental data.The effects of various forms of Cn are thoroughly elucidated via the analysis of the confinement depth,spherical shell thickness,the inner radius,and the smoothing parameters.To find the bound states in the spherically confined endofullerene,the decoupling of the second-order Dirac equation for the large and small components of the radial atomic wave functions is considered.The Dirac equation with the interaction potential is solved numerically by using the Runge-Kutta-Fehlberg method via the decoupling formalism.The influence of spin orientations on the PC and IMF is also elucidated.The effects of spherical confinement,plasma shielding,and the structural properties of the fullerene on the PC and IMF are thoroughly viewed.Moreover,under given physical conditions,the optimal ranges of these effects are determined.
文摘In this paper the macroscopic quantum state of Bose-Einstein condensates in optical lattices is studied by solving the periodic Gross-Pitaevskii equation in one-dimensional geometry. It is shown that an exact solution seen to be a travelling wave of excited macroscopic quantum states resultes in a persistent atom current, which can be controlled by adjusting of the barrier height of the optical periodic potential. A critical condition to generate the travelling wave is demonstrated and we moreover propose a practical experiment to realize the persistent atom current in a toroidal atom waveguide.
基金the National Natural Science Foundation of China(No.30600581)
文摘Objective ：To investigate the different suppressive effect of lidocaine on persistent Na^＋ current and transient Na^＋ current in injured or uninjured dorsal root ganglion neurons. Methods： Totally 23 SD rats were randomly divided into 2 groups： control group （n： 10） and chronically compressed DRG （dorsal root ganglion） group （CCD group, n= 13）. Rats were anesthetized and DRG was isolated. Single DRG neuron was isolated by enzymatic disassociation method. Persistent Na^＋ current （INap） and transient Na^＋ current （INaT） were elicited in voltage clamp mode. Results： The presence of INap was testified in most DRG neurons （38/46 neurons in CCD group and 31/39 neurons in control group, P〉0. 05）. However, the cur- rent density of INap in CCD group （4. 6±0. 6 pA/pF, n=38 neurons） was greater than that in control group （2.5±0.4 pA/pF, n=31 neurons） （P〈0. 05）. The characteristics of INap was observed and found that INap could he blocked by 0.2 μmol/L tetrodotoxin easily. Furthermore, the does-effect relationship of lidocaine on INaP and IN.T were also examined. INaP and IN.T were suppressed by different concentrations of li- docaine, the range for INap was 5-20 μmol/L and for INaT was 0. 05-2 mmol/L. Conclusion： INap and INaT were suppressed by different concentrations of lidocaine. INap was suppressed by very low concentration of lidocaine （5-20 μmol/L）. However, INaT could only be blocked by high concentration of lidocaine （0.05-2 mmol/L）.
文摘The aim of this study was to investigate the effect of hypoxia on the sodium current of rat cardiomyocytes in order to explore ion channel mechanism of cardiomyocyte hypoxia.The rat cardiomyocytes were isolated by acute enzymatic hydrolysis.A group of untreated cells were used to record sodium currents using whole-cell patch-clamp technique,another group was subjected to hypoxia and record sodium currents using same technique.The results showed that the morphological trajectory of sodium hypoxia was not changed compared with that of normal cells.The I-V curve of hypoxic cells was significantly higher than that of normal cells,and the peak current of INa was 15.68%higher than that of normal cells(P<0.0001).Activation potential of normal and hypoxia cells was about-40mV,the maximum peak current corresponds to the stimulation voltage of-25mV.The above results suggest that rat cardiomyocytes sodium current increases in the case of hypoxia.
基金Supported by the Funds for Major Basic Research Project of Sichuan Province under Grant No 02GY029-188, and the Natural Science Foundation of the Committee of Education of Sichuan Province under Grant No 2003A078.
文摘Using an equation of motion technique, we investigate the Kondo effect in a quantum dot coupled to ferromagnetic leads and a mesoscopic ring. It is shown that the Kondo resonance at the Fermi level of the dot presents the periodic change along with the aggrandizement of the magnetic flux and the number of lattice sites NR in the mesoscopic ring, and for the antiparallel spin alignment the Kondo resonances for spin-up and spin-down configurations appear at the same position. However, for the parallel spin alignment, the Kondo resonance splits for the spin-up and spin-down configurations.
基金Supported by the Funds for Major Basic Research Project of Sichuan Province under Grant No 02GY029-188, and the Natural Science Foundation of the Committee of Education of Sichuan Province under Grant No 2003A078.
文摘We investigate the spin-flip process through double quantum dots coupled to two ferromagnetic leads in series. By means of the slave-boson mean-field approximation, we calculate the density of states in the Kondo regime for two different configurations of the leads. It is found that transport shows some remarkable properties depending on the spin-flip strength. These effects may be useful in exploiting the role of electronic correlation in spintronics.
基金Supported by the National Natural Science Foundation of China under Grant No 10347134, and the Youth Foundation of Ningbo under Grant No 2003A62005.
文摘We derive an exact expression for the transmission coefficient through an Aharonov-Bohm ring with a side-coupled quantum dot using the scattering-matrix approach. We show a sudden AB phase change by π as the quantum dot is tuned across the resonance. The Aharonow-Bohm oscillation amplitude can be modulated effectively by tuning the quantum dot level, The transmission coefficient has an expression of the generalized Fano form with a complex Fano parameter q in the presence of the Aharonov-Bohm flux.
基金Supported by Scientific Research Fund of Hunan Provincial Education Department under Grant No.09B079
文摘We theoretically investigate the Kondo effect of a quantum dot embedded in a mesoscopic Aharonov-Bohm （AIR） ring in the presence of the spin flip processes by means of the one-impurity Anderson Hamiltonian. Based on the slave-boson mean-field theory, we find that in this system the persistent current （PC） sensitively depends on the parity and size of the AB ring and can be tuned by the spin-flip scattering （R）. In the small AB ring, the PC is suppressed due to the enhancing R weakening the Kondo resonance. On the contrary, in the large AB ring, with R increasing, the peak of PC firstly moves up to max-peak and then down. Especially, the PC phase shift of π appears suddenly with the proper value of R, implying the existence of the anomalous Kondo effect in this system. Thus this system may be a carldidate for quantum switch.
基金The project supported by the Funds for Major Basic Research Project of Sichuan Province under Grant No. 02GY029-188, and the Natural Science Foundation of the Committee of Education of Sichuan Province under Grant No. 2003 A078,.
文摘We theoretically study the properties of the ground state of the parallel-coupled double quantum dots embedded in a mesoscopic ring in the Kondo regime by means of the two-impurity Anderson Hamiltonian. The Hamiltonian is solved by means of the slave-boson mean-field theory. We find that in this system, the persistent current depends sensitively on both the parity of this system and the size of the ring. In the strong coupling regime, the giant sharp current peak appears, at the same time, the parity dependence of the persistent current disappears. These imply that in the strong coupling regime, there exists giant Kondo resonance and the two dots can be coupled coherently. Thus this system might be a candidate for future device applications.
基金Supported by the Funds for Major Basic Research Project of Sichuan Province under Grant No 02GY029-188, the Natural Science Foundation of the Committee of Education of Sichuan Province under Grant No 2003 A078, and the Scientific Research Fund of Huaihua University.
文摘We theoretically investigate the properties of the ground state of the strongly correlated T-shaped double quantum dots embedded in an Aharonov-Bohm ring in the Kondo regime by means of the one-impurity Anderson Hamiltonian. It is found that in this system, the persistent current depends sensitively on the parity and size of the ring. With the increase of interdot coupling, the persistent current is suppressed due to the enhancing Fano interference weakening the Kondo effect. Moreover, when the spin of quantum dot embedded in the Aharonov- Bohm ring is screened, the persistent current peak is not affected by interdot coupling. Thus this model may be a new candidate for detecting Kondo screening cloud.
基金The project supported by the National Natural Science Foundation of China under Grant Nos. 10574163 and 90306016.Acknowledgments The author wishes to thank Prof. C.G. Bao and Mr. G.M. Huang for their helpful discussions.
文摘A model is proposed to study the quantum rings with two deeply bound electrons under a variable magnetic field. The emphasis is placed to clarify the effect of the size （diameter） and the width of the ring on the fractional Aharonov-Bohm oscillation. It was found that the reduction of size will lead to a very strong oscillation in the ground state energy and in the persistent current. The electronic correlation has also been demonstrated by showing the nodal structures of wave functions.
