Spin-dependent transport properties and Seebeck effects for a crossed graphene superlattice <Emphasis Type="Italic">p-n</Emphasis> junction with armchair edge |
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Authors: | Ben-Hu Zhou Ben-Liang Zhou Yang-Su Zeng Man-Yi Duan Guang-Hui Zhou |
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Institution: | 1.Department of Physics,Shaoyang University,Shaoyang,China;2.Department of Physics and Key Laboratory for Low-Dimensional Structures and Quantum Manipulation (Ministry of Education),Hunan Normal University,Changsha,China;3.College of Physics and Electronic Engineering,Sichuan Normal University,Chengdu,China |
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Abstract: | Using the nonequilibrium Green’s function method combined with the tight-binding Hamiltonian, we theoretically investigate the spin-dependent transmission probability and spin Seebeck coefficient of a crossed armchair-edge graphene nanoribbon (AGNR) superlattice p-n junction under a perpendicular magnetic field with a ferromagnetic insulator, where junction widths W1 of 40 and 41 are considered to exemplify the effect of semiconducting and metallic AGNRs, respectively. A pristine AGNR system is metallic when the transverse layer m = 3j + 2 with a positive integer j and an insulator otherwise. When stubs are present, a semiconducting AGNR junction with width W1 = 40 always shows metallic behavior regardless of the potential drop magnitude, magnetization strength, stub length, and perpendicular magnetic field strength. However, metallic or semiconducting behavior can be obtained from a metallic AGNR junction with W1 = 41 by adjusting these physical parameters. Furthermore, a metal-to-semiconductor transition can be obtained for both superlattice p-n junctions by adjusting the number of periods of the superlattice. In addition, the spin-dependent Seebeck coefficient and spin Seebeck coefficient of the two systems are of the same order of magnitude owing to the appearance of a transmission gap, and the maximum absolute value of the spin Seebeck coefficient reaches 370 µV/K when the optimized parameters are used. The calculated results offer new possibilities for designing electronic or heat-spintronic nanodevices based on the graphene superlattice p-n junction. |
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