Topological zero-line modes(ZLMs) with spin and valley degrees of freedom give rise to spin, valley and spinvalley transport, which support a platform for exploring quantum transport physics and potential applications...Topological zero-line modes(ZLMs) with spin and valley degrees of freedom give rise to spin, valley and spinvalley transport, which support a platform for exploring quantum transport physics and potential applications in spintronic/valleytronic devices. In this work, we investigate the beam-splitting behaviors of the charge current due to the ZLMs in a three-terminal system. We show that with certain combinations of ZLMs, the incident charge current along the interface between different topological phases can be divided into different polarized currents with unit transmittance in two outgoing terminals. As a result, fully spin-polarized, valley-polarized and spin-valley-polarized electron beam splitters are generated. The mechanism of these splitters is attributed to the cooperative effects of the distribution of the ZLMs and the intervalley and intravalley scatterings that are modulated by the wave-vector mismatch and group velocity mismatch. Interestingly, half-quantized transmittance of these scatterings is found in a fully spin-valley-polarized electron beam splitter.Furthermore, the results indicate that these splitters can be applicable to graphene, silicene, germanene and stanene due to their robustness against the spin–orbit coupling. Our findings offer a new way to understand the transport mechanism and investigate the promising applications of ZLMs.展开更多
Inner edge state with spin and valley degrees of freedom is a promising candidate for designing a dissipationless device due to the topological protection. The central challenge for the application of the inner edge s...Inner edge state with spin and valley degrees of freedom is a promising candidate for designing a dissipationless device due to the topological protection. The central challenge for the application of the inner edge state is to generate and modulate the polarized currents. In this work, we discover a new mechanism to generate fully valley-and spin–valley-polarized current caused by the Bloch wavevector mismatch(BWM). Based on this mechanism, we design some serial-typed inner-edge filters. By using once of the BWM, the coincident states could be divided into transmitted and reflected modes, which can serve as a valley or spin–valley filter. In particular, while with twice of the BWM, the incident current is absolutely reflected to support an off state with a specified valley and spin, which is different from the gap effect.These findings give rise to a new platform for designing valleytronics and spin-valleytronics.展开更多
We numerically investigate the valley-polarized current in symmetric and asymmetric zigzag graphene nanoribbons(ZGNRs) by the adiabatic pump, and the effect of spatial symmetry is considered by introducing different p...We numerically investigate the valley-polarized current in symmetric and asymmetric zigzag graphene nanoribbons(ZGNRs) by the adiabatic pump, and the effect of spatial symmetry is considered by introducing different pumping regions. It is found that pumping potentials with the symmetry Vp(x,y) = Vp(-x,y)can generate the largest valleypolarized current. The valley-polarized currents I13~L with the pumping potential symmetry Vp(x,y) =Vp(x,-y,) and I14~L with Vp(x,y) = Vp(-x,-y) of symmetric ZGNRs are much smaller than those of asymmetric ZGNRs. We also find I13~L and I14~L of symmetric ZGNRs decrease and increase with the increasing pumping amplitude, respectively. Moreover, the dephasing effect from the electron-phonon coupling within the Buttiker dephasing scheme is introduced. The valley-polarized current of the symmetric ZGNRs with Vp(x,y)= Vp(x,-y) increases with the increase of the dephasing strength while that with Vp(x,y) = Vp(-x,-y) decreases as the dephasing strength increases.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 12304058, 12204073, and 12147102)Guangxi Science and Technology Base and Talent Project (Grant No. 2022AC21077)+1 种基金Natural Science Foundation of Guangxi Province (Grant No. 2024GXNSFBA010229)Foundation of Guangxi University of Science and Technology (Grant No. 21Z52)。
文摘Topological zero-line modes(ZLMs) with spin and valley degrees of freedom give rise to spin, valley and spinvalley transport, which support a platform for exploring quantum transport physics and potential applications in spintronic/valleytronic devices. In this work, we investigate the beam-splitting behaviors of the charge current due to the ZLMs in a three-terminal system. We show that with certain combinations of ZLMs, the incident charge current along the interface between different topological phases can be divided into different polarized currents with unit transmittance in two outgoing terminals. As a result, fully spin-polarized, valley-polarized and spin-valley-polarized electron beam splitters are generated. The mechanism of these splitters is attributed to the cooperative effects of the distribution of the ZLMs and the intervalley and intravalley scatterings that are modulated by the wave-vector mismatch and group velocity mismatch. Interestingly, half-quantized transmittance of these scatterings is found in a fully spin-valley-polarized electron beam splitter.Furthermore, the results indicate that these splitters can be applicable to graphene, silicene, germanene and stanene due to their robustness against the spin–orbit coupling. Our findings offer a new way to understand the transport mechanism and investigate the promising applications of ZLMs.
基金supported by the National Natural Science Foundation of China (Grant Nos.12204073 and 12147102)the Scientific and Technological Research Program of Chongqing Municipal Education Commission (Grant No.KJQN202303105)+1 种基金the Specific Research Project of Guangxi for Research Bases and Talents (Grant No.2022AC21077)the Foundation of Guangxi University of Science and Technology (Grant No.21Z52)。
文摘Inner edge state with spin and valley degrees of freedom is a promising candidate for designing a dissipationless device due to the topological protection. The central challenge for the application of the inner edge state is to generate and modulate the polarized currents. In this work, we discover a new mechanism to generate fully valley-and spin–valley-polarized current caused by the Bloch wavevector mismatch(BWM). Based on this mechanism, we design some serial-typed inner-edge filters. By using once of the BWM, the coincident states could be divided into transmitted and reflected modes, which can serve as a valley or spin–valley filter. In particular, while with twice of the BWM, the incident current is absolutely reflected to support an off state with a specified valley and spin, which is different from the gap effect.These findings give rise to a new platform for designing valleytronics and spin-valleytronics.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11704190,11874221,and 11504240)the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20171030)
文摘We numerically investigate the valley-polarized current in symmetric and asymmetric zigzag graphene nanoribbons(ZGNRs) by the adiabatic pump, and the effect of spatial symmetry is considered by introducing different pumping regions. It is found that pumping potentials with the symmetry Vp(x,y) = Vp(-x,y)can generate the largest valleypolarized current. The valley-polarized currents I13~L with the pumping potential symmetry Vp(x,y) =Vp(x,-y,) and I14~L with Vp(x,y) = Vp(-x,-y) of symmetric ZGNRs are much smaller than those of asymmetric ZGNRs. We also find I13~L and I14~L of symmetric ZGNRs decrease and increase with the increasing pumping amplitude, respectively. Moreover, the dephasing effect from the electron-phonon coupling within the Buttiker dephasing scheme is introduced. The valley-polarized current of the symmetric ZGNRs with Vp(x,y)= Vp(x,-y) increases with the increase of the dephasing strength while that with Vp(x,y) = Vp(-x,-y) decreases as the dephasing strength increases.
