Based on Duan＇s topological current theory,we show that in a ferromagnetic spin-triplet superconductor there is a topological defect of string structures which can be interpreted as vortex lines.Such defects are diff...Based on Duan＇s topological current theory,we show that in a ferromagnetic spin-triplet superconductor there is a topological defect of string structures which can be interpreted as vortex lines.Such defects are different from the Abrikosov vortices in one-component condensate systems.We investigate the inner topological structure of the vortex lines.The topological charge density,velocity,and topological current of the vortex lines can all be expressed in terms of 未 function,which indicates that the vortices can only arise from the zero points of an order parameter field.The topological charges of vortex lines are quantized in terms of the Hopf indices and Brouwer degrees of-mapping.The divergence of the self-induced magnetic field can be rigorously determined by the corresponding order parameter fields and its expression also takes the form of a 未-like function.Finally,based on the implicit function theorem and the Taylor expansion,we conduct detailed studies on the bifurcation of vortex topological current and find different directions of the bifurcation.展开更多
This paper theoretically studies Josephson spin current through triplet superconductor/ferromagnet/triplet super- conductor junctions. At the ferromagnet/superconductor interfaces, the ferromagnetic scattering potenti...This paper theoretically studies Josephson spin current through triplet superconductor/ferromagnet/triplet super- conductor junctions. At the ferromagnet/superconductor interfaces, the ferromagnetic scattering potential gives rise to coupling between the Andreev bound states and lifts their spin degeneracy. These spin-split Andreev states carry the Josephson spin current through the junctions. The generated spin supercurrent can be controlled by the magnetization of a ferromagnetic thin layer and bias voltage across the junctions.展开更多
Based on Duan’s topological current theory,we show that in a ferromagnetic spin-triplet superconductor there is a topological defect of string structures which can be interpreted as vortex lines.Such defects are diff...Based on Duan’s topological current theory,we show that in a ferromagnetic spin-triplet superconductor there is a topological defect of string structures which can be interpreted as vortex lines.Such defects are different from the Abrikosov vortices in one-component condensate systems.We investigate the inner topological structure of the vortex lines.The topological charge density,velocity,and topological current of the vortex lines can all be expressed in terms of δ function,which indicates that the vortices can only arise from the zero points of an order parameter field.The topological charges of vortex lines are quantized in terms of the Hopf indices and Brouwer degrees of-mapping.The divergence of the self-induced magnetic field can be rigorously determined by the corresponding order parameter fields and its expression also takes the form of a δ-like function.Finally,based on the implicit function theorem and the Taylor expansion,we conduct detailed studies on the bifurcation of vortex topological current and find different directions of the bifurcation.展开更多
With the use of a model Hamiltonian and retarded double time green’s function formalism, we obtain mathematical expressions for spin density wave and superconductivity parameters. The model reveals a distinct possibi...With the use of a model Hamiltonian and retarded double time green’s function formalism, we obtain mathematical expressions for spin density wave and superconductivity parameters. The model reveals a distinct possibility of the coexistence of magnetic phase and superconductivity, which are two usually irreconcilable cooperative phenomena. The work is motivated by the recent experimental evidences of coexistence of spin density wave and superconductivity in a number of FeAs-based superconductors. The theoretical results are then applied to show the coexistence of spin density wave and superconductivity in iron pnictide compound Ba1-xKxFe2As2 (0.2 ≤ x < 0.4).展开更多
Based on the scattering theory, we calculate the Josephson current in a junction between two ferromagnetic super-conductors as a function of the interface potential z. We consider the ferromagnetic superconductor （FS...Based on the scattering theory, we calculate the Josephson current in a junction between two ferromagnetic super-conductors as a function of the interface potential z. We consider the ferromagnetic superconductor （FS） in three different Cooper pairing states： spin singlet s-wave pairing （SWP） state, spin triplet opposite spin pairing （OSP） state, and spin triplet equal spin pairing （ESP） state. We find that the critical Josephson current as a function of z shows clear differences among the SWP, OSP, and ESP states. The obtained results can be used as a useful tool for determining the pair symmetry of the ferromagnetic superconductors.展开更多
In this study, we investigate the tunneling conductance at a finite temperature in a normal metal/ferromagnetic superconductor nano-junction where the ferromagnetic superconductor （FS） is in three different cooper p...In this study, we investigate the tunneling conductance at a finite temperature in a normal metal/ferromagnetic superconductor nano-junction where the ferromagnetic superconductor （FS） is in three different cooper pairing states： spin singlet s-wave pairing （SWP）, spin triplet opposite spin pairing （OSP）, and spin triplet equal spin pairing （ESP） while including Fermi wave mismatch （FWM） and effective mass mismatch （EMM） in two sides of the nano-junction. We find that the conductance shows clearly different behaviors all depending on the symmetries of cooper pairing in a manner that the conductance spectra shows a gap-like structure, two interior dips structure and zero bias peak for SWP, OSP, and ESP, respectively. Also, the effective FS gap （Δeff） is a linear and decreasing function of exchange field. The slope of （Δeff） versus exchange field for OSP is twice the SWP. Thus, we can determine the spin polarization of N/FS nano-junction based on the dependence of （Δeff） to exchange field.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10905026 and 10905027)the Specialized Research Fund for the Doctoral Program of Higher Education(Grant No.20090211120030)the Lanzhou Development of Science and Technology Program,China(Grant No.2010-1-129)
文摘Based on Duan＇s topological current theory,we show that in a ferromagnetic spin-triplet superconductor there is a topological defect of string structures which can be interpreted as vortex lines.Such defects are different from the Abrikosov vortices in one-component condensate systems.We investigate the inner topological structure of the vortex lines.The topological charge density,velocity,and topological current of the vortex lines can all be expressed in terms of 未 function,which indicates that the vortices can only arise from the zero points of an order parameter field.The topological charges of vortex lines are quantized in terms of the Hopf indices and Brouwer degrees of-mapping.The divergence of the self-induced magnetic field can be rigorously determined by the corresponding order parameter fields and its expression also takes the form of a 未-like function.Finally,based on the implicit function theorem and the Taylor expansion,we conduct detailed studies on the bifurcation of vortex topological current and find different directions of the bifurcation.
文摘This paper theoretically studies Josephson spin current through triplet superconductor/ferromagnet/triplet super- conductor junctions. At the ferromagnet/superconductor interfaces, the ferromagnetic scattering potential gives rise to coupling between the Andreev bound states and lifts their spin degeneracy. These spin-split Andreev states carry the Josephson spin current through the junctions. The generated spin supercurrent can be controlled by the magnetization of a ferromagnetic thin layer and bias voltage across the junctions.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10905026 and 10905027)the Specialized Research Fund for the Doctoral Program of Higher Education(Grant No.20090211120030)the Lanzhou Development of Science and Technology Program,China(Grant No.2010-1-129)
文摘Based on Duan’s topological current theory,we show that in a ferromagnetic spin-triplet superconductor there is a topological defect of string structures which can be interpreted as vortex lines.Such defects are different from the Abrikosov vortices in one-component condensate systems.We investigate the inner topological structure of the vortex lines.The topological charge density,velocity,and topological current of the vortex lines can all be expressed in terms of δ function,which indicates that the vortices can only arise from the zero points of an order parameter field.The topological charges of vortex lines are quantized in terms of the Hopf indices and Brouwer degrees of-mapping.The divergence of the self-induced magnetic field can be rigorously determined by the corresponding order parameter fields and its expression also takes the form of a δ-like function.Finally,based on the implicit function theorem and the Taylor expansion,we conduct detailed studies on the bifurcation of vortex topological current and find different directions of the bifurcation.
文摘With the use of a model Hamiltonian and retarded double time green’s function formalism, we obtain mathematical expressions for spin density wave and superconductivity parameters. The model reveals a distinct possibility of the coexistence of magnetic phase and superconductivity, which are two usually irreconcilable cooperative phenomena. The work is motivated by the recent experimental evidences of coexistence of spin density wave and superconductivity in a number of FeAs-based superconductors. The theoretical results are then applied to show the coexistence of spin density wave and superconductivity in iron pnictide compound Ba1-xKxFe2As2 (0.2 ≤ x < 0.4).
基金Project supported by the Iran National Science Foundation(INSF)
文摘Based on the scattering theory, we calculate the Josephson current in a junction between two ferromagnetic super-conductors as a function of the interface potential z. We consider the ferromagnetic superconductor （FS） in three different Cooper pairing states： spin singlet s-wave pairing （SWP） state, spin triplet opposite spin pairing （OSP） state, and spin triplet equal spin pairing （ESP） state. We find that the critical Josephson current as a function of z shows clear differences among the SWP, OSP, and ESP states. The obtained results can be used as a useful tool for determining the pair symmetry of the ferromagnetic superconductors.
文摘In this study, we investigate the tunneling conductance at a finite temperature in a normal metal/ferromagnetic superconductor nano-junction where the ferromagnetic superconductor （FS） is in three different cooper pairing states： spin singlet s-wave pairing （SWP）, spin triplet opposite spin pairing （OSP）, and spin triplet equal spin pairing （ESP） while including Fermi wave mismatch （FWM） and effective mass mismatch （EMM） in two sides of the nano-junction. We find that the conductance shows clearly different behaviors all depending on the symmetries of cooper pairing in a manner that the conductance spectra shows a gap-like structure, two interior dips structure and zero bias peak for SWP, OSP, and ESP, respectively. Also, the effective FS gap （Δeff） is a linear and decreasing function of exchange field. The slope of （Δeff） versus exchange field for OSP is twice the SWP. Thus, we can determine the spin polarization of N/FS nano-junction based on the dependence of （Δeff） to exchange field.
