We propose a four-terminal device consisting of two parallel quantum dots with Rashba spin-orbit interaction （RSOI）, coupled to two side superconductor leads and two common ferromagnetic leads, respectively. The two...We propose a four-terminal device consisting of two parallel quantum dots with Rashba spin-orbit interaction （RSOI）, coupled to two side superconductor leads and two common ferromagnetic leads, respectively. The two ferromagnetic leads and two quantum dots form a ring threaded by Aharonov-Bohm （AB） flux. This device possesses normal quasiparticle transmission between the two ferromagnetic leads, and normal and crossed Andreev reflections providing conductive holes. For the appropriate spin polarization of the ferromagnetic leads, RSOI and AB flux, the pure spin-up （or spin-down） current without net charge current in the right lead, which is due to the equal numbers of electrons and holes with the same spin-polarization moving along the same direction, can be obtained by adjusting the gate voltage, which may be used in practice as a pure spin-current injector.展开更多
A magnetic field-controlled spin-current diode is theoretically proposed,which consists of a junction with an interacting quantum dot sandwiched between a pair of nonmagnetic electrodes.By applying a spin bias VS acro...A magnetic field-controlled spin-current diode is theoretically proposed,which consists of a junction with an interacting quantum dot sandwiched between a pair of nonmagnetic electrodes.By applying a spin bias VS across the junction,a pure spin current can be obtained in a certain gate voltage regime,regardless of whether the Coulomb repulsion energy exists.More interestingly,if we applied an external magnetic field on the quantum dot,we observed a clear asymmetry in the spectrum of spin current IS as a function of spin bias,while the charge current always decays to zero in the Coulomb blockade regime.Such asymmetry in the current profile suggests a spin diode-like behavior with respect to the spin bias,while the net charge through the device is almost zero.Different from the traditional charge current diode,this design can change the polarity direction and rectifying ability by adjusting the external magnetic field,which is very convenient.This device scheme can be compatible with current technologies and has potential applications in spintronics or quantum processing.展开更多
We propose a simple adiabatic quantum spin pump to generate pure spin current. The spin pump is driven by an ac gate voltage and a time-dependent magnetic impurity potential. It is found that the total pumped spin per...We propose a simple adiabatic quantum spin pump to generate pure spin current. The spin pump is driven by an ac gate voltage and a time-dependent magnetic impurity potential. It is found that the total pumped spin per cycle exhibits oscillations, whose magnitude decays exponentially with changing strength of the impurity potential. The proposed method may be useful for spintronic applications.展开更多
Photogalvanic effect(PGE)occurs in materials with non-centrosymmetric structures when irradiated by linearly or circularly polarized light.Here,using non-equilibrium Green’s function combined with density functional ...Photogalvanic effect(PGE)occurs in materials with non-centrosymmetric structures when irradiated by linearly or circularly polarized light.Here,using non-equilibrium Green’s function combined with density functional theory(NEGF-DFT),we investigated the linear photogalvanic effect(LPGE)in monolayers of group-V elements(As,Sb,and Bi)by first-principles calculations.First,by designing a two-probe structure based on the group-V elements,we found a giant anisotropy photoresponse of As between the armchair and zigzag directions.Then,we analyzed Sb and Bi’s charge and spin photocurrent characteristics when considering the spin-orbit coupling(SOC)effect.It is found that when the polarization direction of linearly polarized light is parallel or perpendicular to the transport direction(θ=0°or 90°),the spin up and spin down photoresponse in the armchair direction has the same magnitude and direction,leading to the generation of net charge current.However,in the zigzag direction,the spin up and spin down photoresponse have the same magnitude with opposite directions,leading to the generation of pure spin current.Furthermore,it is understood by analyzing the bulk spin photovoltaic(BSPV)coefficient from the symmetry point of view.Finally,we found that the net charge current generated in the armchair direction and the pure spin current generated in the zigzag direction can be further tuned with the increase of the material’s buckling height.Our results highlight that these group-V monolayers are promising candidates for novel functional materials,which will provide a broad prospect for the realization of ultrathin ferroelectric devices in optoelectronics due to their spontaneous polarization characteristics and high Curie temperature.展开更多
Arbitrary magnetic field modulations to the semiconductor pump with both the Rashba and Dresselhaus spin-orbit couplings （SOC） are studied. The pump is driven by double time-dependent delta potentials, which are for...Arbitrary magnetic field modulations to the semiconductor pump with both the Rashba and Dresselhaus spin-orbit couplings （SOC） are studied. The pump is driven by double time-dependent delta potentials, which are formed in the interfaces between the semiconductor region and two normal leads. Based on the Floquet scattering approach, our calculations show that various currents can be pumped by couplings of the magnetic fields and the SOCs. Pure spin currents modulated by the arbitrary magnetic fields are discussed in detail.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 10775091,10774094,10974124,and 11047172)the Excellent Youth and Midlife Scientist Scientific Research Encouragement Foundation of Shandong Province,China(Grant No. BS2010DS006)the Doctor Research Startup Foundation of Linyi University,China (Grant No. BS201023)
文摘We propose a four-terminal device consisting of two parallel quantum dots with Rashba spin-orbit interaction （RSOI）, coupled to two side superconductor leads and two common ferromagnetic leads, respectively. The two ferromagnetic leads and two quantum dots form a ring threaded by Aharonov-Bohm （AB） flux. This device possesses normal quasiparticle transmission between the two ferromagnetic leads, and normal and crossed Andreev reflections providing conductive holes. For the appropriate spin polarization of the ferromagnetic leads, RSOI and AB flux, the pure spin-up （or spin-down） current without net charge current in the right lead, which is due to the equal numbers of electrons and holes with the same spin-polarization moving along the same direction, can be obtained by adjusting the gate voltage, which may be used in practice as a pure spin-current injector.
基金Project supported by the National Natural Science Foundation of China(Grant No.11404322)the Natural Science Foundation of Huai’an(Grant No.HAB202150).
文摘A magnetic field-controlled spin-current diode is theoretically proposed,which consists of a junction with an interacting quantum dot sandwiched between a pair of nonmagnetic electrodes.By applying a spin bias VS across the junction,a pure spin current can be obtained in a certain gate voltage regime,regardless of whether the Coulomb repulsion energy exists.More interestingly,if we applied an external magnetic field on the quantum dot,we observed a clear asymmetry in the spectrum of spin current IS as a function of spin bias,while the charge current always decays to zero in the Coulomb blockade regime.Such asymmetry in the current profile suggests a spin diode-like behavior with respect to the spin bias,while the net charge through the device is almost zero.Different from the traditional charge current diode,this design can change the polarity direction and rectifying ability by adjusting the external magnetic field,which is very convenient.This device scheme can be compatible with current technologies and has potential applications in spintronics or quantum processing.
基金supported by the State Key Program for Basic Research of China(Grant Nos.2015CB921202,2014CB921103,2011CB922103,and 2010CB923400)the National Natural Science Foundation of China(Grant Nos.11225420,11174125,and 91021003)the Priority Academic Program Development of Higher Education Institutions of Jiangsu Province,China
文摘We propose a simple adiabatic quantum spin pump to generate pure spin current. The spin pump is driven by an ac gate voltage and a time-dependent magnetic impurity potential. It is found that the total pumped spin per cycle exhibits oscillations, whose magnitude decays exponentially with changing strength of the impurity potential. The proposed method may be useful for spintronic applications.
基金support from the National Key R&D Program of China under Grant No.2022YFA1404003the National Natural Science Foundation of China (Grant Nos.12074230 and 12174231)+2 种基金the Natural Science Foundation of Shanxi Normal Universitythe Fund for Shanxi“1331 Project”Shanxi Province 100-Plan Talent Program,Fundamental Research Program of Shanxi Province through 202103021222001 and 202203021212397.
文摘Photogalvanic effect(PGE)occurs in materials with non-centrosymmetric structures when irradiated by linearly or circularly polarized light.Here,using non-equilibrium Green’s function combined with density functional theory(NEGF-DFT),we investigated the linear photogalvanic effect(LPGE)in monolayers of group-V elements(As,Sb,and Bi)by first-principles calculations.First,by designing a two-probe structure based on the group-V elements,we found a giant anisotropy photoresponse of As between the armchair and zigzag directions.Then,we analyzed Sb and Bi’s charge and spin photocurrent characteristics when considering the spin-orbit coupling(SOC)effect.It is found that when the polarization direction of linearly polarized light is parallel or perpendicular to the transport direction(θ=0°or 90°),the spin up and spin down photoresponse in the armchair direction has the same magnitude and direction,leading to the generation of net charge current.However,in the zigzag direction,the spin up and spin down photoresponse have the same magnitude with opposite directions,leading to the generation of pure spin current.Furthermore,it is understood by analyzing the bulk spin photovoltaic(BSPV)coefficient from the symmetry point of view.Finally,we found that the net charge current generated in the armchair direction and the pure spin current generated in the zigzag direction can be further tuned with the increase of the material’s buckling height.Our results highlight that these group-V monolayers are promising candidates for novel functional materials,which will provide a broad prospect for the realization of ultrathin ferroelectric devices in optoelectronics due to their spontaneous polarization characteristics and high Curie temperature.
基金supported by the Startup Fund for Doctor of Hunan University of Arts and Science (No. 10133004)supported by the Research Foundation of Education Bureau of Hunan Province (No. 14C0807)
文摘Arbitrary magnetic field modulations to the semiconductor pump with both the Rashba and Dresselhaus spin-orbit couplings （SOC） are studied. The pump is driven by double time-dependent delta potentials, which are formed in the interfaces between the semiconductor region and two normal leads. Based on the Floquet scattering approach, our calculations show that various currents can be pumped by couplings of the magnetic fields and the SOCs. Pure spin currents modulated by the arbitrary magnetic fields are discussed in detail.
