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
We have studied the characteristics of current-induced nonequilibrium spin polarization in semiconductor-nanowire/swave superconductor junctions with strong spin–orbit coupling. It was found that within some paramete...We have studied the characteristics of current-induced nonequilibrium spin polarization in semiconductor-nanowire/swave superconductor junctions with strong spin–orbit coupling. It was found that within some parameter regions the magnitude of the current-induced nonequilibrium spin polarization density in such structures will increase（or decrease） with the decrease（or increase） of the charge current density, in contrast to that found in normal spin–orbit coupled semiconductor structures. It was also found that the unusual characteristics of the current-induced nonequilibrium spin polarization in such structures can be well explained by the effect of the Andreev reflection.展开更多
The possibility of cooling a system from liquid helium temperature, 4.2 K, using a tunnel junction refrigerator is analysed. Calculations show that the device can be used over a wide temperature range from 4 K down to...The possibility of cooling a system from liquid helium temperature, 4.2 K, using a tunnel junction refrigerator is analysed. Calculations show that the device can be used over a wide temperature range from 4 K down to well below 1 mK with necessary cooling power. However, several serious difficulties must be overcome before the method can be used in low temperature laboratories.展开更多
We study the temperature T and the phase of the Josephson critical current I(φ)by taking into account theroughness scattering effect at inerface in an f-wave superconductor(S)/Insulator layer(I)/f-wave superconductor...We study the temperature T and the phase of the Josephson critical current I(φ)by taking into account theroughness scattering effect at inerface in an f-wave superconductor(S)/Insulator layer(I)/f-wave superconductor(S)junction.It is found that the Josephson critical currents in f-wave S/f-wave S,the barrier strength and the roughnessstrength at inerface always suppress the Andreev reflection.When α=β,the phase dependence of the Josephson currentI(φ)between two f-wave S is predicted to be simφ;particularly,when α≠β,the phase dependence of the Josephsoncurrent I(φ)between two f-wave superconductors is not predicted to be sin φ and with the barrier strength increasing,the period of the I((φ)turns decrease.展开更多
The Josephson effect in the superconductor/ferromagnet/superconductor （SFS） graphene Josephson junction is studied using the Dirac Bogoliubov-de Gennes （DBdG） formalism. It is shown that the SFS graphene junction ...The Josephson effect in the superconductor/ferromagnet/superconductor （SFS） graphene Josephson junction is studied using the Dirac Bogoliubov-de Gennes （DBdG） formalism. It is shown that the SFS graphene junction drives 0–π transition with the increasing of p=h0L/vF？, which captures the effects of both the exchange field and the length of the junction; the spin-down current is dominant. The 0 state is stable for p 〈 pc （critical value pc ≈ 0.80） and the π state is stable for p 〉 pc, where the free energy minima are at φg=0 and φg=π, respectively. The coexistence of the 0 and π states appears in the vicinity of pc.展开更多
The Andreev-like levels and the free energy of the spin superconductor/insulator/spin superconductor junction are obtained by using the Bogoliubov-de Gennes equation. The phase dependence of the spin supercurrents exh...The Andreev-like levels and the free energy of the spin superconductor/insulator/spin superconductor junction are obtained by using the Bogoliubov-de Gennes equation. The phase dependence of the spin supercurrents exhibits a 0-π transition by changing the barrier strength. The dependences of the critical current on the barrier strength and the temperature are also presented.展开更多
In this paper, a dc Josephson junction between borocarbide superconductors has been studied theoretically. The s＋g-wave pairing symmetry which is observed in rare earth complex of borocarbides has a huge anisotropy a...In this paper, a dc Josephson junction between borocarbide superconductors has been studied theoretically. The s＋g-wave pairing symmetry which is observed in rare earth complex of borocarbides has a huge anisotropy and is an interesting form of unconventional superconductivity. We calculate the Josephson current in a superconductorinsulator-superconductor （SIS） Josephson junction with s＋g-wave superconducting pairing symmetry. In our planar junction c-axis is parallel to an interface with finite transparency but ab-planes of two tetragonal superconductors are misorientated by angle α. We obtain that the Josephson current is strongly dependent on mis-orientation between the left and the right ab-planes. An insulator sandwiched between two superconductors which acts as a potential barrier is demonstrated by a transparency coefficient. The effects of the potential barrier and the mis-orientation on the current are studied analytically and numerically. Occurrence of 0-θ transition in this s＋g-wave junction is investigated in this paper. A comparison between d-wave Josephson junction and s＋g-wave one is also made in the present paper.展开更多
Nonequilibrium effect due to the imbalance in the number of the ? and ? spin electrons has been studied for the tunneling currents in the ferromagnet-insulator-superconductor (FIS) tunneling junctions within a phenome...Nonequilibrium effect due to the imbalance in the number of the ? and ? spin electrons has been studied for the tunneling currents in the ferromagnet-insulator-superconductor (FIS) tunneling junctions within a phenomenological manner. It has been stated how the nonequilibrium effect should be observed in the spin-polarized quasiparticle tunneling currents, and pointed out that the detectable nonequilibrium effect could be found in the FIS tunneling junction at 77 K using HgBa2Ca2Cu3O8+? (Hg-1223) high-Tc superconductor rather than Bi2Sr2CaCu2O8+? (Bi-2212) one.展开更多
Mesa-structured submicron intrinsic Josephson junctions are successfully fabricated and well characterized on underdoped Bi2Sr2Ca1-xYxCu2O8＋δ single crystals with a Tc of 80 K. Tunneling spectra at the temperatures ...Mesa-structured submicron intrinsic Josephson junctions are successfully fabricated and well characterized on underdoped Bi2Sr2Ca1-xYxCu2O8＋δ single crystals with a Tc of 80 K. Tunneling spectra at the temperatures ranging from 4.2 K to 295 K are measured. A pulse technique is used to reduce sample heating for the measurement near pseudogap opening temperature T^＊ - 280 K. Our experimental results show that the superconducting gap, the peakdip separation, and the pseudogap opening temperature are all increased as compared with those from near optimally doped samples, which requires further theoretical analysis in the future.展开更多
In this paper, we discuss the full counting statistics of superconducting quantum dot contacts. We discuss the effects both of phonon and onsite electronic interaction focusing on the experimentally most relevant case...In this paper, we discuss the full counting statistics of superconducting quantum dot contacts. We discuss the effects both of phonon and onsite electronic interaction focusing on the experimentally most relevant case of strong onsite electronic interactions. We find that in general, the Josephson effect and multiple Andreev reflections in these systems are strongly suppressed due to the onsite interaction. However, in case resonant phonons are found, the effect of the onsite interaction can be overcome.展开更多
The anisotropy of the dc Josephson current in the superconducting junctions of the p-wave equal spin pairing symmetry is theoretically investigated by the Furusaki Tsukada-like formula. The current phase relations exh...The anisotropy of the dc Josephson current in the superconducting junctions of the p-wave equal spin pairing symmetry is theoretically investigated by the Furusaki Tsukada-like formula. The current phase relations exhibit different oscillation periods and different phase shifts for the current along different directions, respectively.展开更多
The critical current density behaviors across a bicrystal grain boundary（GB） inclined to the current direction with different angles in YBa2Cu3O7-δ bicrystal junctions in magnetic fields are investigated.There are...The critical current density behaviors across a bicrystal grain boundary（GB） inclined to the current direction with different angles in YBa2Cu3O7-δ bicrystal junctions in magnetic fields are investigated.There are two main reasons for the difference in critical current density in junctions at different GB inclined angles in the same magnetic field：（i） the GB plane area determines the current carrying cross section;（ii） the vortex motion dynamics at the GB affects the critical current value when the vortex starts to move along the GB by Lorentz force.Furthermore,the vortex motion in a bicrystal GB is studied by investigating transverse（Hall） and longitudinal current–voltage characteristics（I–Vxx and I–Vxy）.It is found that the I–Vxx curve diverges from linearity at a high driving current,while the I–Vxy curve keeps nearly linear,which indicates the vortices inside the GB break out of the GB by Lorentz force.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Project supported by the National Natural Science Foundation of China(Grant No.11474106)
文摘We have studied the characteristics of current-induced nonequilibrium spin polarization in semiconductor-nanowire/swave superconductor junctions with strong spin–orbit coupling. It was found that within some parameter regions the magnitude of the current-induced nonequilibrium spin polarization density in such structures will increase（or decrease） with the decrease（or increase） of the charge current density, in contrast to that found in normal spin–orbit coupled semiconductor structures. It was also found that the unusual characteristics of the current-induced nonequilibrium spin polarization in such structures can be well explained by the effect of the Andreev reflection.
文摘The possibility of cooling a system from liquid helium temperature, 4.2 K, using a tunnel junction refrigerator is analysed. Calculations show that the device can be used over a wide temperature range from 4 K down to well below 1 mK with necessary cooling power. However, several serious difficulties must be overcome before the method can be used in low temperature laboratories.
基金Supported by the"333"Project Funds of Jiangsu Province of China,the National Natural Science Foundation of China under Grant No.20571029by the Program for Excellent Talents in Huangshi Institute of Technology
文摘We study the temperature T and the phase of the Josephson critical current I(φ)by taking into account theroughness scattering effect at inerface in an f-wave superconductor(S)/Insulator layer(I)/f-wave superconductor(S)junction.It is found that the Josephson critical currents in f-wave S/f-wave S,the barrier strength and the roughnessstrength at inerface always suppress the Andreev reflection.When α=β,the phase dependence of the Josephson currentI(φ)between two f-wave S is predicted to be simφ;particularly,when α≠β,the phase dependence of the Josephsoncurrent I(φ)between two f-wave superconductors is not predicted to be sin φ and with the barrier strength increasing,the period of the I((φ)turns decrease.
基金Project supported by the National Natural Science Foundation of China(Grant No.11074088)
文摘The Josephson effect in the superconductor/ferromagnet/superconductor （SFS） graphene Josephson junction is studied using the Dirac Bogoliubov-de Gennes （DBdG） formalism. It is shown that the SFS graphene junction drives 0–π transition with the increasing of p=h0L/vF？, which captures the effects of both the exchange field and the length of the junction; the spin-down current is dominant. The 0 state is stable for p 〈 pc （critical value pc ≈ 0.80） and the π state is stable for p 〉 pc, where the free energy minima are at φg=0 and φg=π, respectively. The coexistence of the 0 and π states appears in the vicinity of pc.
基金Project supported by the National Key R&D Program of China(Grant No.2017YFA0303203)the National Natural Science Foundation of China(Grant No.11474149)
文摘The Andreev-like levels and the free energy of the spin superconductor/insulator/spin superconductor junction are obtained by using the Bogoliubov-de Gennes equation. The phase dependence of the spin supercurrents exhibits a 0-π transition by changing the barrier strength. The dependences of the critical current on the barrier strength and the temperature are also presented.
文摘In this paper, a dc Josephson junction between borocarbide superconductors has been studied theoretically. The s＋g-wave pairing symmetry which is observed in rare earth complex of borocarbides has a huge anisotropy and is an interesting form of unconventional superconductivity. We calculate the Josephson current in a superconductorinsulator-superconductor （SIS） Josephson junction with s＋g-wave superconducting pairing symmetry. In our planar junction c-axis is parallel to an interface with finite transparency but ab-planes of two tetragonal superconductors are misorientated by angle α. We obtain that the Josephson current is strongly dependent on mis-orientation between the left and the right ab-planes. An insulator sandwiched between two superconductors which acts as a potential barrier is demonstrated by a transparency coefficient. The effects of the potential barrier and the mis-orientation on the current are studied analytically and numerically. Occurrence of 0-θ transition in this s＋g-wave junction is investigated in this paper. A comparison between d-wave Josephson junction and s＋g-wave one is also made in the present paper.
文摘Nonequilibrium effect due to the imbalance in the number of the ? and ? spin electrons has been studied for the tunneling currents in the ferromagnet-insulator-superconductor (FIS) tunneling junctions within a phenomenological manner. It has been stated how the nonequilibrium effect should be observed in the spin-polarized quasiparticle tunneling currents, and pointed out that the detectable nonequilibrium effect could be found in the FIS tunneling junction at 77 K using HgBa2Ca2Cu3O8+? (Hg-1223) high-Tc superconductor rather than Bi2Sr2CaCu2O8+? (Bi-2212) one.
基金Project supported by the National Natural Science Foundation of China(Grant No.10974242)
文摘Mesa-structured submicron intrinsic Josephson junctions are successfully fabricated and well characterized on underdoped Bi2Sr2Ca1-xYxCu2O8＋δ single crystals with a Tc of 80 K. Tunneling spectra at the temperatures ranging from 4.2 K to 295 K are measured. A pulse technique is used to reduce sample heating for the measurement near pseudogap opening temperature T^＊ - 280 K. Our experimental results show that the superconducting gap, the peakdip separation, and the pseudogap opening temperature are all increased as compared with those from near optimally doped samples, which requires further theoretical analysis in the future.
文摘In this paper, we discuss the full counting statistics of superconducting quantum dot contacts. We discuss the effects both of phonon and onsite electronic interaction focusing on the experimentally most relevant case of strong onsite electronic interactions. We find that in general, the Josephson effect and multiple Andreev reflections in these systems are strongly suppressed due to the onsite interaction. However, in case resonant phonons are found, the effect of the onsite interaction can be overcome.
基金Project supported by the National Natural Science Foundation of China(Grant No.10504011)the State Key Program for Basic Research of China(Grant Nos.2006CB921803 and 2009CB929504)
文摘The anisotropy of the dc Josephson current in the superconducting junctions of the p-wave equal spin pairing symmetry is theoretically investigated by the Furusaki Tsukada-like formula. The current phase relations exhibit different oscillation periods and different phase shifts for the current along different directions, respectively.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61501222,61371036,and 61571219)the School Scientific Research Fund of Nanjing Institute of Technology,China(Grant Nos.YKJ201418)
文摘The critical current density behaviors across a bicrystal grain boundary（GB） inclined to the current direction with different angles in YBa2Cu3O7-δ bicrystal junctions in magnetic fields are investigated.There are two main reasons for the difference in critical current density in junctions at different GB inclined angles in the same magnetic field：（i） the GB plane area determines the current carrying cross section;（ii） the vortex motion dynamics at the GB affects the critical current value when the vortex starts to move along the GB by Lorentz force.Furthermore,the vortex motion in a bicrystal GB is studied by investigating transverse（Hall） and longitudinal current–voltage characteristics（I–Vxx and I–Vxy）.It is found that the I–Vxx curve diverges from linearity at a high driving current,while the I–Vxy curve keeps nearly linear,which indicates the vortices inside the GB break out of the GB by Lorentz force.
