arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1605.07155cond-mat.mes-hallcond-mat.mtrl-sci
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拓扑绝缘体Bi2Se3和InAs Rashba态电流诱导自旋极化的直接比较

Direct comparison of current-induced spin polarization in topological insulator Bi2Se3 and InAs Rashba states

Connie H. Li, Olaf M. J. van t Erve, Shivani Rajput, Lian Li, Berry T. Jonker

摘要:

三维拓扑绝缘体(TI)具有时间反转对称性保护的线性色散狄拉克表面态。在TI表面的能带弯曲也可能导致共存的平凡的二维电子气(2DEG)状态与抛物线的能量色散,存在作为自旋分裂对由于Rashba自旋轨道耦合(SOC)。一个偏置电流预计将产生自旋极化在这两个系统所产生的螺旋自旋动量锁定。然而,它们的诱导自旋极化预计在幅度和符号上都不同。在这里,我们比较偏置电流产生的自旋极化在Bi2Se3(111)膜狄拉克表面状态与平凡的2DEG状态共存的自旋电位测量,与相同的测量InAs(001)样品,只有平凡的2DEG状态存在。我们观察到自旋极化所产生的自旋动量锁定在这两种情况下,相反的符号的自旋电压。我们提出了一个模型的基础上自旋相关的电化学势直接推导出预期的TI表面状态的迹象,并明确地表明,占主导地位的贡献电流产生的自旋极化测量的TI是从狄拉克表面状态。Dirac和Rashba 2DEG状态的螺旋自旋纹理的这种直接电访问是朝着下一代基于TI和SOC的量子器件中的自旋的电操纵迈出的一步。

英文摘要:

Three-dimensional topological insulators (TIs) exhibit time-reversal symmetry protected, linearly dispersing Dirac surface states. Band bending at the TI surface may also lead to coexisting trivial two-dimensional electron gas (2DEG) states with parabolic energy dispersion that exist as spin-split pairs due to Rashba spin-orbit coupling (SOC). A bias current is expected to generate spin polarization in both systems arising from their helical spin-momentum locking. However, their induced spin polarization is expected to be different in both magnitude and sign. Here, we compare spin potentiometric measurements of bias current-generated spin polarization in Bi2Se3(111) films where Dirac surface states coexist with trivial 2DEG states, with identical measurements on InAs(001) samples where only trivial 2DEG states are present. We observe spin polarization arising from spin-momentum locking in both cases, with opposite signs of the spin voltage. We present a model based on spin dependent electrochemical potentials to directly derive the signs expected for the TI surface states, and unambiguously show that the dominant contribution to the current-generated spin polarization measured in the TI is from the Dirac surface states. This direct electrical access of the helical spin texture of Dirac and Rashba 2DEG states is an enabling step towards the electrical manipulation of spins in next generation TI and SOC based quantum devices.

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