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
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
High temperature superconducting(HTS)magnets conduct DC currents ranging from hundreds to tens of thousands of amperes.To achieve such DC output amplitudes,conventional power supplies are unsuitable,owing to their ext...High temperature superconducting(HTS)magnets conduct DC currents ranging from hundreds to tens of thousands of amperes.To achieve such DC output amplitudes,conventional power supplies are unsuitable,owing to their extreme cost,energy consumption,and bulkiness.The indispensable current leads of conventional power supplies carrying large DC current cause an extra heat leakage into the cryogenic system,thus increasing the number of required cryocoolers.A potential solution to tackle this problem,however,is to use HTS flux pumps that inject a large amount of DC current into the HTS magnet in a wireless fashion,thereby eliminating the need for current leads,and allow the magnets to work in the quasi‐persistent current mode.Compared with the conventional power supplies,the flux pumps offer the advantages of low cost,low energy consumption,and compact size,etc.,which essentially have broad application prospects in nuclear magnetic resonance(NMR/MRI),fusion,particle accelerators,superconducting electric machine,maglev train,etc.Over the last decade,a variety of HTS flux pumps have been invented with improved DC outputs,reaching over kiloamperes.Moreover,those flux pumps have different working principles,structures and operation strategies.In this paper,we provide an in‐depth review on the HTS flux pumps developed in the last decade.In particular,for the HTS travelling wave flux pumps and HTS transformer‐rectifier flux pumps,the discussions are focused on their working principles and technical advances.In the end,we discuss the present applications of HTS flux pumps,along with their potential future applications.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
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
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
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.
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 National Natural Science Foundation of China under grant numbers 51877143the Science and Technology Project of Sichuan Province,China under grant number 2021YFS0088。
文摘High temperature superconducting(HTS)magnets conduct DC currents ranging from hundreds to tens of thousands of amperes.To achieve such DC output amplitudes,conventional power supplies are unsuitable,owing to their extreme cost,energy consumption,and bulkiness.The indispensable current leads of conventional power supplies carrying large DC current cause an extra heat leakage into the cryogenic system,thus increasing the number of required cryocoolers.A potential solution to tackle this problem,however,is to use HTS flux pumps that inject a large amount of DC current into the HTS magnet in a wireless fashion,thereby eliminating the need for current leads,and allow the magnets to work in the quasi‐persistent current mode.Compared with the conventional power supplies,the flux pumps offer the advantages of low cost,low energy consumption,and compact size,etc.,which essentially have broad application prospects in nuclear magnetic resonance(NMR/MRI),fusion,particle accelerators,superconducting electric machine,maglev train,etc.Over the last decade,a variety of HTS flux pumps have been invented with improved DC outputs,reaching over kiloamperes.Moreover,those flux pumps have different working principles,structures and operation strategies.In this paper,we provide an in‐depth review on the HTS flux pumps developed in the last decade.In particular,for the HTS travelling wave flux pumps and HTS transformer‐rectifier flux pumps,the discussions are focused on their working principles and technical advances.In the end,we discuss the present applications of HTS flux pumps,along with their potential future applications.
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.
