We theoretically investigate possible quantum Hall phases and corresponding edge states in graphene by taking a strong magnetic field, Zeeman splitting M, and sublattice potential △ into account but without spin–orb...We theoretically investigate possible quantum Hall phases and corresponding edge states in graphene by taking a strong magnetic field, Zeeman splitting M, and sublattice potential △ into account but without spin–orbit interaction. It was found that for the undoped graphene either a quantum valley Hall phase or a quantum spin Hall phase emerges in the system, depending on relative magnitudes of M and △. When the Fermi energy deviates from the Dirac point, the quantum spin-valley Hall phase appears and its characteristic edge state is contributed only by one spin and one valley species. The metallic boundary states bridging different quantum Hall phases possess a half-integer quantized conductance, like e^2/2h or3e^2/2h. The possibility of tuning different quantum Hall states with M and △ suggests possible graphene-based spintronics and valleytronics applications.展开更多
We investigate the electron transport in silicene with both staggered electric potential and magnetization; the latter comes from the magnetic proximity effect by depositing silicene on a magnetic insulator. It is sho...We investigate the electron transport in silicene with both staggered electric potential and magnetization; the latter comes from the magnetic proximity effect by depositing silicene on a magnetic insulator. It is shown that the silicene could be a spin and valley half metal under appropriate parameters when the spin–orbit interaction is considered; further, the filtered spin and valley could be controlled by modulating the staggered potential or magnetization. It is also found that in the spin-valve structure of silicene, not only can the antiparallel magnetization configuration significantly reduce the valve-structure conductance, but the reversing staggered electric potential can cause a high-performance magnetoresistance due to the spin and valley blocking effects. Our findings show that the silicene might be an ideal basis for the spin and valley filter analyzer devices.展开更多
We investigate the spin-dependent electron transport in single and double normal/ferromagnetic/normal zigzag graphene nanoribbon （NG/FG/NG） junctions. The ferromagnetism in the FG region originates from the spontane...We investigate the spin-dependent electron transport in single and double normal/ferromagnetic/normal zigzag graphene nanoribbon （NG/FG/NG） junctions. The ferromagnetism in the FG region originates from the spontaneous magnetization of the zigzag graphene nanoribbon. It is shown that when the zigzag-chain number of the ribbon is even and only a single transverse mode is actived, the single NG/FG/NG junction can act as a spin polarizer and/or a spin analyzer because of the valley selection rule and the spin-exchange field in the FG, while the double NG/FG/NG/FG/NG junction exhibits a quantum switching effect, in which the on and the off states switch rapidly by varying the cross angle between two FG magnetizations. Our findings may shed light on the application of magnetized graphene nanoribbons to spintronics devices.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.1144721811274059+1 种基金11404278and 11447216)
文摘We theoretically investigate possible quantum Hall phases and corresponding edge states in graphene by taking a strong magnetic field, Zeeman splitting M, and sublattice potential △ into account but without spin–orbit interaction. It was found that for the undoped graphene either a quantum valley Hall phase or a quantum spin Hall phase emerges in the system, depending on relative magnitudes of M and △. When the Fermi energy deviates from the Dirac point, the quantum spin-valley Hall phase appears and its characteristic edge state is contributed only by one spin and one valley species. The metallic boundary states bridging different quantum Hall phases possess a half-integer quantized conductance, like e^2/2h or3e^2/2h. The possibility of tuning different quantum Hall states with M and △ suggests possible graphene-based spintronics and valleytronics applications.
基金Project supported by the National Natural Science Foundation of China （Grant Nos. 11074032, 11074233, and 11274079） and the Natural Science Foundation of Jiangsu Province, China （Grant No. BK20131284）.
文摘We investigate the electron transport in silicene with both staggered electric potential and magnetization; the latter comes from the magnetic proximity effect by depositing silicene on a magnetic insulator. It is shown that the silicene could be a spin and valley half metal under appropriate parameters when the spin–orbit interaction is considered; further, the filtered spin and valley could be controlled by modulating the staggered potential or magnetization. It is also found that in the spin-valve structure of silicene, not only can the antiparallel magnetization configuration significantly reduce the valve-structure conductance, but the reversing staggered electric potential can cause a high-performance magnetoresistance due to the spin and valley blocking effects. Our findings show that the silicene might be an ideal basis for the spin and valley filter analyzer devices.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.110704032 and 110704033)the Natural Science Foundation of Jiangsu Province,China(Grant No.BK2010416)the National Basic Research Program of China(Grant No.2009CB945504)
文摘We investigate the spin-dependent electron transport in single and double normal/ferromagnetic/normal zigzag graphene nanoribbon （NG/FG/NG） junctions. The ferromagnetism in the FG region originates from the spontaneous magnetization of the zigzag graphene nanoribbon. It is shown that when the zigzag-chain number of the ribbon is even and only a single transverse mode is actived, the single NG/FG/NG junction can act as a spin polarizer and/or a spin analyzer because of the valley selection rule and the spin-exchange field in the FG, while the double NG/FG/NG/FG/NG junction exhibits a quantum switching effect, in which the on and the off states switch rapidly by varying the cross angle between two FG magnetizations. Our findings may shed light on the application of magnetized graphene nanoribbons to spintronics devices.
