Conversion between spin and charge currents with topological insulators

Abstract

Injection of a spin current into the surface or interface states of a topological insulator (TI) induces a charge current (inverse Edelstein effect or IEE) and, inversely, a charge current flowing at the surface or interface states of a TI generates a nonzero spin density (Edelstein Effect or EE) from which a spin current can be ejected into an adjacent layer. The parameters characterizing the efficiency of these conversions between spin and charge currents have been derived in recent experiments. By using a spinor distribution function for a momentum-spin locked TI, we determine a number of spin transport properties of TI-based heterostructure and find that the spin to charge conversion in IEE is controlled by the relaxation of an out-of equilibrium distribution in the TI states while the charge to spin conversion in EE depends on the electron transmission rate at the interface of the TI.

Study of Surface Spin-Polarized Electron Accumulation in Topological Insulators Using Scanning Tunneling Microscopy

“…As illustrated by Figure 4(b), this monotonic increase is linear in nature, which may be attributed to the greater accumulation of spinpolarized electrons on the sample surface in the case of larger bias currents. The above observation is consistent with theoretical calculations of the charge-spin conversion efficiency 46 for TIs, which suggest the spinaccumulation linearly depends on the magnitude of the bias current. Figure 5 illustrates the measurement of spin-polarized electron accumulation for one fixed direction of bias current using clean W tips.…”

Anomalous Nonlocal Resistance and Spin-Charge Conversion Mechanisms in Two-Dimensional Metals

“…However, many materials of interest in spintronics have large CISP effects [17,18] arising from Rashba SOC. This is especially so in (quasi) 2D materials with broken inversion symmetry, such as the surfaces states of 3D topological insulators [19,20], gold-hybridized graphene [21,22] and Bi/Ag quantum wells [23]. Recently, a great deal of effort has been put into nonlocal transport experiments on adatom-functionalized graphene [8,9,24,25], which is predicted to exhibit strong Rashba SOC [26][27][28][29][30].…”

Dirac-surface-state-dominated spin to charge current conversion in the topological insulator ( Bi0.22Sb0.78)2Te3Mendes1, Santos2, Holanda3 et al. 2017Phys. Rev. B583271View full textAdd to dashboardCite

“…We follow Refs. [8,[44][45][46][47][48][49][50] and interpret the spin-to-charge conversion in the TI layer as arising from the inverse Edelstein effect (IEE), which has its origin in the spin-momentum locking in the Fermi contours due to the Rashba SOC interaction. The 3D spin current in Eq.…”

“…The 3D spin current in Eq. (2) flows into the TI layer and is converted by the IEE into a lateral charge current with a 2D density j C = (2e/h)λ IEE J S , where λ IEE is a coefficient characterizing the IEE, with the dimension of length and proportional to the Rashba coefficient, and hence to the magnitude of the SOC [8,[44][45][46]. The measured voltage is related to this current density by V IEE = R S wj C , where R S is the shunt resistance, w the width of the (Bi,Sb)Te/Py bilayer in the length of the Py layer, and j C has units of A/m.…”

“…The direct Edelstein effect and the inverse Edelstein effect (IEE) are made possible by the Rashba effect that arises from SOC and broken inversion symmetry at material surfaces and interfaces [42][43][44][45]. The Rashba field produces spin-momentum locking in the electron Fermi contours that enables the conversion between spin and charge currents.…”