Electrical Detection of the Spin Polarization Due to Charge Flow in the Surface State of the Topological Insulator Bi1.5Sb0.5Te1.7Se1.3

Ando, Yoshinori; Hamasaki, Takahiro; Kurokawa, Takayuki; Ichiba, K.; Yang, Fan; Novak, Mario; Sasaki, Satoshi; Segawa, Kouji; Ando, Yoichi; Shiraishi, Masashi

doi:10.1021/nl502546c

Cited by 164 publications

(179 citation statements)

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“…4 corresponds to the spin injection efficiency η [17]. The obtained value is η ≈ 6.0 × 10 −4 (0.06%), which is comparable to the values reported for bulk-insulating BSTS samples [17,22]. In summary, we measured spin-electricity conversion induced by spin pumping into Sn-doped Bi 2 Te 2 Se at low temperatures.…”

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confidence: 81%

“…On the surface states of TIs, since spin direction and electron-flow direction have oneto-one correspondence (the spin-momentum locking), injected spins are converted into electric currents along an in-plane direction on the surface, when the bulk state is sufficiently insulating. Although highly efficient spinelectricity conversion has been reported for bulk-metallic TIs [9,10,16], the reported value for bulk-insulating BSTS is ∼ 0.01% [17,22].Though the spin-electricity conversion on the topological surface states was demonstrated using a spin pumping technique [17], it remains unclear how the produced electric signal is related to surface transport properties of TI materials. In this manuscript, we study spin-electricity conversion induced by spin pumping for several SnBTS samples whose bulk insulating properties are ideal for its detailed study.…”

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confidence: 99%

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Universal scaling for the spin-electricity conversion on surface states of topological insulators

et al. 2016

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We have investigated spin-electricity conversion on surface states of bulk-insulating topological insulator (TI) materials using a spin pumping technique. The sample structure is Ni-Fe|Cu|TI trilayers, in which magnetic proximity effects on the TI surfaces are negligibly small owing to the inserted Cu layer. Voltage signals produced by the spin-electricity conversion are clearly observed, and enhanced with decreasing temperature in line with the dominated surface transport at lower temperatures. The efficiency of the spin-electricity conversion is greater for TI samples with higher resistivity of bulk states and longer mean free path of surface states, consistent with the surface spin-electricity conversion.Injection and detection of non-equilibrium spins are key techniques in the field of spintronics [1]. A powerful method to inject spins is spin pumping. Spin pumping enables dynamical spin injection from a ferromagnet into an adjacent non-magnetic metal, which is induced by coherent precession of magnetization at ferromagnetic resonance (FMR) [2]. In spin pumping experiments, bilayers comprising ferromagnetic Ni 81 Fe 19 (permalloy, Py) and nonmagnetic Pt have been studied as a typical system [2-6]. Though Pt has been widely used for spin detection owing to its strong spin-orbit interaction, search of more efficient spin detectors is one of the urgent issues in the spintronics field [7,8].A topological insulator (TI) is a promising material for spintronics application because of its potential for highly efficient spin-electricity conversion [9,10]. Topological insulators are a state of quantum matter [11][12][13], in which the surface is metallic, while the interior is insulating. Spin-electricity conversion on TI materials has recently been investigated using spin pumping for bulk-metallic samples (Bi 2 Se 3 ) [14][15][16] and also for bulk-insulating ones [17]. In a previous report [17], some authors of the present paper demonstrated the spinelectricity conversion induced by spin pumping into surface states of TIs, Bi 1.5 Sb 0.5 Te 1.7 Se 1.3 (BSTS) [18,19] and Sn-doped Bi 2 Te 2 Se (SnBTS) [20] in contact with Py. Since millimeter-thick TI samples were used in [17], the inverse spin Hall signal from bulk carriers are neglected and the observed spin-electricity conversion signal was safely ascribed to a surface contribution. The sign of * K. T. Yamamoto and Y. Shiomi contributed equally to this work.† Corresponding author; Electronic address: shiomi@imr.tohoku.ac.jp the generated electric signals is consistent with the spinelectricity conversion on the topological surface state, whereas the opposite sign is expected for co-existing Rashba surface states [21]. On the surface states of TIs, since spin direction and electron-flow direction have oneto-one correspondence (the spin-momentum locking), injected spins are converted into electric currents along an in-plane direction on the surface, when the bulk state is sufficiently insulating. Although highly efficient spinelectricity conversion has been reported fo...

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Universal scaling for the spin-electricity conversion on surface states of topological insulators

et al. 2016

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“…In the surface of TIs as well as the Rashbasplitting 2D electron gas (2DEG), the helical band structure is realized, in which the spin and momentum are locked and hence the surface currents are spin polarized [18][19][20]. The interface between a TI (or a Rashba 2DEG [21]) and a ferromagnet can be a spin source in which the SOC enhances the magnitude of both charge and spin currents [22][23][24][25]. Electric transport properties of bilayers of 3D TIs with (metallic) ferromagnets have indeed been interpreted in terms of much larger spin Hall angles [26,27].…”

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Magnetic-proximity-induced magnetoresistance on topological insulators

2017

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We theoretically study the magnetoresistance (MR) of two-dimensional massless Dirac electrons as found on the surface of three-dimensional topological insulators (TIs) that are capped by a ferromagnetic insulator (FI). We calculate charge and spin transport by Kubo and Boltzmann theories, taking into account the ladder-vertex correction and the in-scattering due to normal and magnetic disorder. The induced exchange splitting is found to generate an electric conductivity that depends on the magnetization orientation, but its form is very different from both the anisotropic and the spin Hall MR. The in-plane MR vanishes identically for nonmagnetic disorder, while out-of-plane magnetizations cause a large MR ratio. On the other hand, we do find an in-plane MR and planar Hall effect in the presence of magnetic disorder aligned with the FI magnetization. Our results may help us understand recent transport measurements on TI|FI systems.

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“…[7][8][9][10][11][12][13][14][15] In Bi 2 Se 3 systems, bulk-insulating samples are obtained by chemical substitution, e.g. Sb substitution in Bi sites and Te substitution in Se sites.…”

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Linear magnetoresistance in a topological insulator Ru2Sn3

Shiomi

Saitoh

2017

AIP Advances

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We have studied magnetotransport properties of a topological insulator material Ru2Sn3. Bulk single crystals of Ru2Sn3 were grown by a Bi flux method. The resistivity is semiconducting at high temperatures above 160 K, while it becomes metallic below 160 K. Nonlinear field dependence of Hall resistivity in the metallic region shows conduction of multiple carriers at low temperatures. In the high-temperature semiconducting region, magnetoresistance exhibits a conventional quadratic magnetic-field dependence. In the low-temperature metallic region, however, high-field magnetoresistance is clearly linear with magnetic fields, signaling a linear dispersion in the low-temperature electronic structure. Small changes in the magnetoresistance magnitude with respect to the magnetic field angle indicate that bulk electron carriers are responsible mainly for the observed linear magnetoresistance.

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Electrical Detection of the Spin Polarization Due to Charge Flow in the Surface State of the Topological Insulator Bi_1.5Sb_0.5Te_1.7Se_1.3

Cited by 164 publications

References 31 publications

Universal scaling for the spin-electricity conversion on surface states of topological insulators

Universal scaling for the spin-electricity conversion on surface states of topological insulators

Magnetic-proximity-induced magnetoresistance on topological insulators

Linear magnetoresistance in a topological insulator Ru2Sn3

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