The Ising spin–orbit coupling could give rise to the spin-triplet Cooper pairs and equal-spin Andreev reflection(AR)in Ising superconductors.Here we theoretically study the valley-dependent equal-spin AR in a ferroma...The Ising spin–orbit coupling could give rise to the spin-triplet Cooper pairs and equal-spin Andreev reflection(AR)in Ising superconductors.Here we theoretically study the valley-dependent equal-spin AR in a ferromagnet/Ising superconductor junction with a circularly polarized light applied to the ferromagnet.Because of the spin-triplet Cooper pairs and the optical irradiation,eight kinds of AR processes appear in the junction,including equal-spin AR and normal AR,the strengths and properties of which strongly depend on the valley degree of freedom.The AR probabilities for the incident electron from the two valleys exhibit certain symmetry with respect to the magnetization angle and the effective energy of light.The equal-spin AR and normal AR present different features and resonant behaviors near the superconducting gap edges.Due to equal-spin-triplet Cooper pairs,not only charge supercurrent but also spin supercurrent can transport in the Ising superconductors.The differential spin conductance for electron injecting from the two valleys can be controlled by the circularly polarized light.展开更多
The construction of BESⅢ detector has been finished and the data taking is under plan. Some physics topics on charmonium decays at BESIII experiment are discussed in this paper. The measurement of properties of ηc a...The construction of BESⅢ detector has been finished and the data taking is under plan. Some physics topics on charmonium decays at BESIII experiment are discussed in this paper. The measurement of properties of ηc and η′c at BESⅢ is discussed and the expected precision of the measurement is estimated based on BOSS. Also the XcJ decay and the measurement of hyperon decay parameters are mentioned.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
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
Based on the complex three-component order parameter model of a spin-triplet superconductor, by using the C-mapping theory, we derive a new equation describing the distribution of the magnetic field for vortices, whic...Based on the complex three-component order parameter model of a spin-triplet superconductor, by using the C-mapping theory, we derive a new equation describing the distribution of the magnetic field for vortices, which can be reduced to the modified London equation in the case of ｜ψ^2｜^2 ^- ｜ψ^3｜^2 = 0 and Wl^1= 1. A magnetic flux quantization condition for vortices in a spin-triplet superconductor is also derived, which is topological-invariant. Fhrthermore, the branch processes during the evolution of the vortices in a spin-triplet superconductor are discussed. We also point out that the sum of the magnetic flux quantization that those vortices carried is 2nФo （Фo is the unit magnetic flux）, that is to say, the sum of winding number is even, which needs to be proved by experiment.展开更多
We propose a scheme to reveal the possible nematic superconducting order parameter in the doped Bi2Se3 by observing the anisotropic unconventional Josephson effect without an external magnetic field.We find the presen...We propose a scheme to reveal the possible nematic superconducting order parameter in the doped Bi2Se3 by observing the anisotropic unconventional Josephson effect without an external magnetic field.We find the presence of an intrinsicπ-phase in the spin-triplet channel of Andreev reflection.Its competition with the odd-parity superconducting gap phase can lead to unconventional Josephson effect in the Josephson junction,whose normal region is connected to the same side of the superconductor,called the U-shaped junction according to its geometry.For Josephson junctions with the interfaces perpendicular to the nematic direction,the competition will lead to a Josephsonπ-junctions.In the case where the interface is parallel to the nematic direction,it will lead to a Josephson 0-junction.Thus,this can directly reflect the nematic superconductivity.It is worth noting that Josephson coupling with the 4πperiod appears only in the normal injected channels.Interestingly,if the Josephson junction adopts a conventional geometry,it always exhibits a normal Josephson 0-junction regardless of the gap function taken by the doped Bi2Se3 and therefore cannot distinguish the pairing symmetry.We thus propose a superconducting quantum interference device containing a U-shaped Josephson junction to detect nematic superconductivity.This proposal not only can be applied to detect nematic superconductivity but also provides a feasible platform for topological quantum computation.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
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
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11974153,12374034 and 11921005)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302403)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB28000000)。
文摘The Ising spin–orbit coupling could give rise to the spin-triplet Cooper pairs and equal-spin Andreev reflection(AR)in Ising superconductors.Here we theoretically study the valley-dependent equal-spin AR in a ferromagnet/Ising superconductor junction with a circularly polarized light applied to the ferromagnet.Because of the spin-triplet Cooper pairs and the optical irradiation,eight kinds of AR processes appear in the junction,including equal-spin AR and normal AR,the strengths and properties of which strongly depend on the valley degree of freedom.The AR probabilities for the incident electron from the two valleys exhibit certain symmetry with respect to the magnetization angle and the effective energy of light.The equal-spin AR and normal AR present different features and resonant behaviors near the superconducting gap edges.Due to equal-spin-triplet Cooper pairs,not only charge supercurrent but also spin supercurrent can transport in the Ising superconductors.The differential spin conductance for electron injecting from the two valleys can be controlled by the circularly polarized light.
基金National Natural Science Foundation of China(10491303)100 Talents Program of CAS(U-25)
文摘The construction of BESⅢ detector has been finished and the data taking is under plan. Some physics topics on charmonium decays at BESIII experiment are discussed in this paper. The measurement of properties of ηc and η′c at BESⅢ is discussed and the expected precision of the measurement is estimated based on BOSS. Also the XcJ decay and the measurement of hyperon decay parameters are mentioned.
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.
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.
基金supported by National Natural Science Foundation of China and Cuiying Programme of Lanzhou University
文摘Based on the complex three-component order parameter model of a spin-triplet superconductor, by using the C-mapping theory, we derive a new equation describing the distribution of the magnetic field for vortices, which can be reduced to the modified London equation in the case of ｜ψ^2｜^2 ^- ｜ψ^3｜^2 = 0 and Wl^1= 1. A magnetic flux quantization condition for vortices in a spin-triplet superconductor is also derived, which is topological-invariant. Fhrthermore, the branch processes during the evolution of the vortices in a spin-triplet superconductor are discussed. We also point out that the sum of the magnetic flux quantization that those vortices carried is 2nФo （Фo is the unit magnetic flux）, that is to say, the sum of winding number is even, which needs to be proved by experiment.
基金the Ministry of Science and Technology of China(Grant No.2016YFA0401003)the National Natural Science Foundation of China(Grant No.11674114).
文摘We propose a scheme to reveal the possible nematic superconducting order parameter in the doped Bi2Se3 by observing the anisotropic unconventional Josephson effect without an external magnetic field.We find the presence of an intrinsicπ-phase in the spin-triplet channel of Andreev reflection.Its competition with the odd-parity superconducting gap phase can lead to unconventional Josephson effect in the Josephson junction,whose normal region is connected to the same side of the superconductor,called the U-shaped junction according to its geometry.For Josephson junctions with the interfaces perpendicular to the nematic direction,the competition will lead to a Josephsonπ-junctions.In the case where the interface is parallel to the nematic direction,it will lead to a Josephson 0-junction.Thus,this can directly reflect the nematic superconductivity.It is worth noting that Josephson coupling with the 4πperiod appears only in the normal injected channels.Interestingly,if the Josephson junction adopts a conventional geometry,it always exhibits a normal Josephson 0-junction regardless of the gap function taken by the doped Bi2Se3 and therefore cannot distinguish the pairing symmetry.We thus propose a superconducting quantum interference device containing a U-shaped Josephson junction to detect nematic superconductivity.This proposal not only can be applied to detect nematic superconductivity but also provides a feasible platform for topological quantum computation.
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).
