The extra heat generation in spin transport is usually interpreted in terms of the spin relaxation. Reformulating the heat generation rate, we find alternative current-force pairs without cross effects, which enable u...The extra heat generation in spin transport is usually interpreted in terms of the spin relaxation. Reformulating the heat generation rate, we find alternative current-force pairs without cross effects, which enable us to interpret the product of each pair as a distinct mechanism of heat generation. The results show that the spin-dependent part of the heat generation includes two terms. One is proportional to the square of the spin accumulation and arises from the spin relaxation. However, the other is proportional to the square of the spin-accumulation gradient and should be attributed to another mechanism, the spin diffusion. We illustrate the characteristics of the two mechanisms in a typical spin valve with a finite nonmagnetic spacer layer.展开更多
Recently, spin-momentum-locked topological surface states（SSs） have attracted significant attention in spintronics.Owing to spin-momentum locking, the direction of the spin is locked at right angles with respect to ...Recently, spin-momentum-locked topological surface states（SSs） have attracted significant attention in spintronics.Owing to spin-momentum locking, the direction of the spin is locked at right angles with respect to the carrier momentum.In this paper, we briefly review the exotic transport properties induced by topological SSs in topological-insulator（TI）nanostructures, which have larger surface-to-volume ratios than those of bulk TI materials. We discuss the electrical spin generation in TIs and its effect on the transport properties. A current flow can generate a pure in-plane spin polarization on the surface, leading to a current-direction-dependent magnetoresistance in spin valve devices based on TI nanostructures.A relative momentum shift of two coupled topological SSs also generates net spin polarization and induces an in-plane anisotropic negative magnetoresistance. Therefore, the spin-momentum locking can enable the broad tuning of the spin transport properties of topological devices for spintronic applications.展开更多
Efficient generation of spin polarization is very important for spintronics and quantum computation. In chiral materials without magnetic order nor spin-orbit coupling, we find a new spin selectivity effect—chiral ph...Efficient generation of spin polarization is very important for spintronics and quantum computation. In chiral materials without magnetic order nor spin-orbit coupling, we find a new spin selectivity effect—chiral phonon activated spin Seebeck(CPASS)effect. Starting with the nonequilibrium distribution of chiral phonons under a temperature gradient, the CPASS coefficients are computed based on the Boltzmann transport theory. With both the phonon-drag and band transport contributions, the spin accumulations generated by the CPASS effect exhibit quadratic dependence on the temperature gradient. The strength of the CPASS effect and the relative magnitude of both contributions are tunable by the chemical potential modulation. The CPASS effect, which gives a promising explanation on the traditional chiral-induced spin selectivity effect, provides opportunities for the exploration of advanced spintronic devices based on chiral materials even in the absence of any magnetic order and spin-orbit coupling.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 11404013,11605003,61405003,11174020 and 11474012the Scientific Research Project of Beijing Educational Committee under Grant No KM201510011002the 2016 Graduate Research Program of Beijing Technology and Business University
文摘The extra heat generation in spin transport is usually interpreted in terms of the spin relaxation. Reformulating the heat generation rate, we find alternative current-force pairs without cross effects, which enable us to interpret the product of each pair as a distinct mechanism of heat generation. The results show that the spin-dependent part of the heat generation includes two terms. One is proportional to the square of the spin accumulation and arises from the spin relaxation. However, the other is proportional to the square of the spin-accumulation gradient and should be attributed to another mechanism, the spin diffusion. We illustrate the characteristics of the two mechanisms in a typical spin valve with a finite nonmagnetic spacer layer.
基金Project supported by the National Key Basic Research Program of China(Grant Nos.2014CB921103 and 2017YFA0206304)the National Natural Science Foundation of China(Grant Nos.61822403,11874203,U1732159,and U1732273)+1 种基金Fundamental Research Funds for the Central Universities,China(Grant No.021014380080)Collaborative Innovation Center of Solid-State Lighting and Energy-Saving Electronics,China
文摘Recently, spin-momentum-locked topological surface states（SSs） have attracted significant attention in spintronics.Owing to spin-momentum locking, the direction of the spin is locked at right angles with respect to the carrier momentum.In this paper, we briefly review the exotic transport properties induced by topological SSs in topological-insulator（TI）nanostructures, which have larger surface-to-volume ratios than those of bulk TI materials. We discuss the electrical spin generation in TIs and its effect on the transport properties. A current flow can generate a pure in-plane spin polarization on the surface, leading to a current-direction-dependent magnetoresistance in spin valve devices based on TI nanostructures.A relative momentum shift of two coupled topological SSs also generates net spin polarization and induces an in-plane anisotropic negative magnetoresistance. Therefore, the spin-momentum locking can enable the broad tuning of the spin transport properties of topological devices for spintronic applications.
基金supported by the National Natural Science Foundation of China (Grant Nos. 12374044, 11904173, 11890703, and 12275133)supported by the Jiangsu Specially-Appointed Professor Program+1 种基金supported by the National Key R&D Project from Ministry of Science and Technology of China (Grant No. 2022YFA1203100)the “Shuangchuang” Doctor Program of Jiangsu Province (Grant No.JSS-CBS20210341)。
文摘Efficient generation of spin polarization is very important for spintronics and quantum computation. In chiral materials without magnetic order nor spin-orbit coupling, we find a new spin selectivity effect—chiral phonon activated spin Seebeck(CPASS)effect. Starting with the nonequilibrium distribution of chiral phonons under a temperature gradient, the CPASS coefficients are computed based on the Boltzmann transport theory. With both the phonon-drag and band transport contributions, the spin accumulations generated by the CPASS effect exhibit quadratic dependence on the temperature gradient. The strength of the CPASS effect and the relative magnitude of both contributions are tunable by the chemical potential modulation. The CPASS effect, which gives a promising explanation on the traditional chiral-induced spin selectivity effect, provides opportunities for the exploration of advanced spintronic devices based on chiral materials even in the absence of any magnetic order and spin-orbit coupling.
