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 investigate the spin-flip process through double quantum dots coupled to two half-metallic ferromagnetic leads in series. By means of the slave-boson mean-field approximation, we calculate the density of states in ...We investigate the spin-flip process through double quantum dots coupled to two half-metallic 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 the 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
Aharonov-Casher oscillasions of transmission through a mesoscopic ring with a magnetic impurity is investigated. Both spin-dependent transmission and reflection coefficients of spin-state electrons at zero-temperature...Aharonov-Casher oscillasions of transmission through a mesoscopic ring with a magnetic impurity is investigated. Both spin-dependent transmission and reflection coefficients of spin-state electrons at zero-temperature are calculated as a function of the textured electric fields and its title angle in the present of spin-flipper scattering. It is found that the spin-exchange interaction can destroy intermittently periodic oscillations of spin-up transmission and reflection coefficients within some small ranges in the adiabatic region of quantum phase. However spin-down transmission and reflection coefficients appear periodic AC oscillations. The calculated results manifest that spindown transmission and reflection coefficients have the same perfect oscillation patterns. In the nonadiabatic region, the behavior of the anomalous AC oscillations are depedent on the difference between the tilt angle of spin and that of texture electric field.展开更多
Tb1-xTmxFeO3(x = 0.00,0.15,0.25) polycrystalline series were synthesized using a solid-state reaction.Our results show that all three prepared samples are in a distorted orthogonal structure and their space group is p...Tb1-xTmxFeO3(x = 0.00,0.15,0.25) polycrystalline series were synthesized using a solid-state reaction.Our results show that all three prepared samples are in a distorted orthogonal structure and their space group is pbnm.When the Tm3+doping amount increases,the characteristics of the spin-flip of the sample decreases following an initial increase at the beginning;the antiferromagnetic property almost reaches zero;the magnetization decreases at the beginning but increases later on.The maximum magnetic entropy change and magnetic refrigeration effect RCP are reduced at varying degrees.Under a 7 T magnetic field,the maximum magnetic entropy change,△Smax,for the three samples of Tb1-xTmxFeO3 with x=0.00,0.15,0.25 is 13.78,-9.28,and 10.69 J/(K·kg),respectively;the magnetic refrigeration capacity(RCP) is 316.85,175.2,and 297.60 J/kg,respectively.In summary,doping with the element Tm reduces △Smax and RCP of the sample.Since the maximum magnetic entropy change and the cooling capacity for the three samples are relatively large,they can be used as an alternative for magnetic refrigerants.展开更多
Based on the algebraic equation of motion(AEOM)approach,we have studied the single-impurity Anderson model by analytically solving the AEOM of the f-electron one-particle Green function in the Kondo limit.The related ...Based on the algebraic equation of motion(AEOM)approach,we have studied the single-impurity Anderson model by analytically solving the AEOM of the f-electron one-particle Green function in the Kondo limit.The related spectral function satisfies the sum rule and shows that there is a well-known three-peak structure at zero temperature.In the low energy limit,we obtain the analytical formula of the Kondo temperature that is the same as the exact solution in form except for a prefactor.We also show that the shape of the Kondo resonance is the Lorentzian form and the corresponding weight is proportional to the spin-flip correlation function.展开更多
Recently experiments and theories show that the tunnel magnetoresistance （TMR） does not only depend on the ferromagnetic metal electrodes but also on the insulator. Considering the rough-scattering effect and spin-f...Recently experiments and theories show that the tunnel magnetoresistance （TMR） does not only depend on the ferromagnetic metal electrodes but also on the insulator. Considering the rough-scattering effect and spin-flip effect in the insulator, this paper investigates the TMR ratio in a ferromagnet/insulator/ferromagnet （FM/I/FM） tunnelling junction by using Slonczewsik＇s model. A more general expression of TMR ratio as a function of barrier height, interface roughness and spin-flip effect is obtained. In lower barrier case, it shows that the TMR ratio depends on the roughscattering effect and spin-flip effect.展开更多
The tunneling conductance and tunneling magnetoresistance(TMR)are investigated in ferromagnet/insulator/ferromagnet/insulator/d-wave superconductor(FM/I/FM/I/d-wave SC)structures by applying an extended Blonder-Tinkha...The tunneling conductance and tunneling magnetoresistance(TMR)are investigated in ferromagnet/insulator/ferromagnet/insulator/d-wave superconductor(FM/I/FM/I/d-wave SC)structures by applying an extended Blonder-Tinkham-Klapwijk(BTK)approach.We study the effects of the exchange splitting in the FM, the magnetic impurity scattering in the thin insulator interface of FM/I/FM,and noncollinear magnetizations in adja- cent magnetic layers on the TMR.It is shown(1)that the tunneling conductance and TMR exhibit amplitude-varying oscillating behavior with exchange splitting,(2)that with the presence of spin-flip scattering in insulator interface of FM/I/FM,the TMR can be dramatically enhanced,and(3)that the TMR depends strongly on the angle between the magnetization of two FMs.展开更多
It was first proposed that an extended chain Ising （ECI） model contains the Ising chain model, single spin doublewell potentials and a pure phonon heat bath of a specific energy exchange with the spins. The extensio...It was first proposed that an extended chain Ising （ECI） model contains the Ising chain model, single spin doublewell potentials and a pure phonon heat bath of a specific energy exchange with the spins. The extension method is easy to apply to high dimensional cases. Then the single spin-flip probability （rate） of the ECI model is deduced based on the Boltzmann principle and general statistical principles of independent events and the model is simplified to an extended chain Glauber-Ising （ECGI） model. Moreover, the relaxation dynamics of the ECGI model were simulated by the Monte Carlo method and a comparison with the predictions of the special chain Clauber-Ising （SCGI） model was presented. It was found that the results of the two models are consistent with each other when the Ising chain length is large enough and temperature is relative low, which is the most valuable case of the model applications. These show that the ECI model will provide a firm physical base for the widely used single spin-flip rate proposed by Glauber and a possible route to obtain the single spin-flip rate of other form and even the multi-spin-flip rate.展开更多
Spin-dependent transmission coefficients as a function of Fermi energy is calculated for electron scattering from magnetic impurity in a narrow quantum wire, in which spin-exchange interaction between conducting elect...Spin-dependent transmission coefficients as a function of Fermi energy is calculated for electron scattering from magnetic impurity in a narrow quantum wire, in which spin-exchange interaction between conducting electron and the impurity leads to exchange spin-flip scattering. Transmission in the spin-flipped channels is explicitly calculated. It has been found that spin-up and spin-down transmission coefficients for intrasubband and intersubband enhance Fano-resonance profiles, which have asymmetric behaviors, whenever Fermi energy crosses bottom of every subband below. Meanwhile due to dephasing of electron wave caused by spin-flip scattering, the entanglement between spin states of electron and magnetic impurity obviously destroys the global step structure of quantized conductance and suppresses the height of the conductance step.展开更多
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Project supported by Scientific Research Fund of Sichuan Provincial Education Department of China (Grant No 2006A069)Funds for Major Basic Research Project of Sichuan Province, China (Grant No 2006J13-155)
文摘We investigate the spin-flip process through double quantum dots coupled to two half-metallic 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 the 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.
文摘Aharonov-Casher oscillasions of transmission through a mesoscopic ring with a magnetic impurity is investigated. Both spin-dependent transmission and reflection coefficients of spin-state electrons at zero-temperature are calculated as a function of the textured electric fields and its title angle in the present of spin-flipper scattering. It is found that the spin-exchange interaction can destroy intermittently periodic oscillations of spin-up transmission and reflection coefficients within some small ranges in the adiabatic region of quantum phase. However spin-down transmission and reflection coefficients appear periodic AC oscillations. The calculated results manifest that spindown transmission and reflection coefficients have the same perfect oscillation patterns. In the nonadiabatic region, the behavior of the anomalous AC oscillations are depedent on the difference between the tilt angle of spin and that of texture electric field.
基金the National Natural Science Foundation of China(11164019,51562032,61565013)Inner Mongolia Natural Science Foundation of China(2015MS0101,2015MS0109)+2 种基金Inner Mongolia Institute of Science and Technology Key Project Fund(NJZZ11166,NJZY16237,NJZY12202)Board Project(201522011)Natural Science Foundation of Henan Province(182300410248)。
文摘Tb1-xTmxFeO3(x = 0.00,0.15,0.25) polycrystalline series were synthesized using a solid-state reaction.Our results show that all three prepared samples are in a distorted orthogonal structure and their space group is pbnm.When the Tm3+doping amount increases,the characteristics of the spin-flip of the sample decreases following an initial increase at the beginning;the antiferromagnetic property almost reaches zero;the magnetization decreases at the beginning but increases later on.The maximum magnetic entropy change and magnetic refrigeration effect RCP are reduced at varying degrees.Under a 7 T magnetic field,the maximum magnetic entropy change,△Smax,for the three samples of Tb1-xTmxFeO3 with x=0.00,0.15,0.25 is 13.78,-9.28,and 10.69 J/(K·kg),respectively;the magnetic refrigeration capacity(RCP) is 316.85,175.2,and 297.60 J/kg,respectively.In summary,doping with the element Tm reduces △Smax and RCP of the sample.Since the maximum magnetic entropy change and the cooling capacity for the three samples are relatively large,they can be used as an alternative for magnetic refrigerants.
基金Project supported by the National Natural Science Foundation of China(Grant No.11974420)。
文摘Based on the algebraic equation of motion(AEOM)approach,we have studied the single-impurity Anderson model by analytically solving the AEOM of the f-electron one-particle Green function in the Kondo limit.The related spectral function satisfies the sum rule and shows that there is a well-known three-peak structure at zero temperature.In the low energy limit,we obtain the analytical formula of the Kondo temperature that is the same as the exact solution in form except for a prefactor.We also show that the shape of the Kondo resonance is the Lorentzian form and the corresponding weight is proportional to the spin-flip correlation function.
基金Project supported by the Program for Excellent Talents in Huaiyin Teachers College
文摘Recently experiments and theories show that the tunnel magnetoresistance （TMR） does not only depend on the ferromagnetic metal electrodes but also on the insulator. Considering the rough-scattering effect and spin-flip effect in the insulator, this paper investigates the TMR ratio in a ferromagnet/insulator/ferromagnet （FM/I/FM） tunnelling junction by using Slonczewsik＇s model. A more general expression of TMR ratio as a function of barrier height, interface roughness and spin-flip effect is obtained. In lower barrier case, it shows that the TMR ratio depends on the roughscattering effect and spin-flip effect.
基金The project supported by Natural Science Foundation of the Education Bureau of Jiangsu Province of China under Grant No.01KJB140007the“333”Program of Jiangsu Province of China
文摘The tunneling conductance and tunneling magnetoresistance(TMR)are investigated in ferromagnet/insulator/ferromagnet/insulator/d-wave superconductor(FM/I/FM/I/d-wave SC)structures by applying an extended Blonder-Tinkham-Klapwijk(BTK)approach.We study the effects of the exchange splitting in the FM, the magnetic impurity scattering in the thin insulator interface of FM/I/FM,and noncollinear magnetizations in adja- cent magnetic layers on the TMR.It is shown(1)that the tunneling conductance and TMR exhibit amplitude-varying oscillating behavior with exchange splitting,(2)that with the presence of spin-flip scattering in insulator interface of FM/I/FM,the TMR can be dramatically enhanced,and(3)that the TMR depends strongly on the angle between the magnetization of two FMs.
基金supported by the National Natural Science Foundation of China (Grant Nos.10774064 and 30860076)Xinjiang High-Tech Development Foundation (Grant No.200916126)the Key Natural Science Foundation of Xinjiang Science-Technology Department (Grant Nos.200821104 and 200821184)
文摘It was first proposed that an extended chain Ising （ECI） model contains the Ising chain model, single spin doublewell potentials and a pure phonon heat bath of a specific energy exchange with the spins. The extension method is easy to apply to high dimensional cases. Then the single spin-flip probability （rate） of the ECI model is deduced based on the Boltzmann principle and general statistical principles of independent events and the model is simplified to an extended chain Glauber-Ising （ECGI） model. Moreover, the relaxation dynamics of the ECGI model were simulated by the Monte Carlo method and a comparison with the predictions of the special chain Clauber-Ising （SCGI） model was presented. It was found that the results of the two models are consistent with each other when the Ising chain length is large enough and temperature is relative low, which is the most valuable case of the model applications. These show that the ECI model will provide a firm physical base for the widely used single spin-flip rate proposed by Glauber and a possible route to obtain the single spin-flip rate of other form and even the multi-spin-flip rate.
文摘Spin-dependent transmission coefficients as a function of Fermi energy is calculated for electron scattering from magnetic impurity in a narrow quantum wire, in which spin-exchange interaction between conducting electron and the impurity leads to exchange spin-flip scattering. Transmission in the spin-flipped channels is explicitly calculated. It has been found that spin-up and spin-down transmission coefficients for intrasubband and intersubband enhance Fano-resonance profiles, which have asymmetric behaviors, whenever Fermi energy crosses bottom of every subband below. Meanwhile due to dephasing of electron wave caused by spin-flip scattering, the entanglement between spin states of electron and magnetic impurity obviously destroys the global step structure of quantized conductance and suppresses the height of the conductance step.
