Topological insulator based spin valve devices: evidence for spin polarized transport of spin-momentum-locked topological surface states

Abstract

Spin-momentum helical locking is one of the most important properties of the nontrivial topological surface states (TSS) in 3D topological insulators (TI). It underlies the iconic topological protection (suppressing elastic backscattering) of TSS and is foundational to many exotic physics (eg., majorana fermions) and device applications (eg., spintronics) predicted for TIs. Based on this spin-momentum locking, a current flowing on the surface of a TI would be spin-polarized in a characteristic in-plane direction perpendicular to the current, and the spin-polarization would reverse when the current direction reverses. Observing such a spin-helical current in transport measurements is a major goal in TI research and applications. We report spin-dependent transport measurements in spin valve devices fabricated from exfoliated thin flakes of Bi2Se3 (a prototype 3D TI) with ferromagnetic (FM) Ni contacts. Applying an in-plane magnetic (B) field to polarize the Ni contacts along their easy axis, we observe an asymmetry in the hysteretic magnetoresistance (MR) between opposite B field directions. The polarity of the asymmetry in MR can be reversed by reversing the direction of the DC current. The observed asymmetric MR can be understood as a spin-valve effect between the current-induced spin polarization on the TI surface (due to spin-momentum-locking of TSS) and the spin-polarized ferromagnetic contacts. Our results provide a direct transport evidence for the spin helical current in TSS.

arXiv comment10 pages, 3 figures

References in corpus (23)

• Topological Insulators
• Topological insulators and superconductors
• Spintronics: Fundamentals and applications
• Superconducting proximity effect and Majorana fermions at the surface of a topological insulator
• Topological Insulators in Three Dimensions
• Discovery (theoretical prediction and experimental observation) of a large-gap topological-insulator class with spin-polarized single-Dirac-cone on the surface
• Topological Field Theory of Time-Reversal Invariant Insulators
• Electronic spin transport and spin precession in single graphene layers at room temperature
• Topological invariants of time-reversal-invariant band structures
• First observation of Spin-Momentum Helical Locking in Bi2Se3 and Bi2Te3, demonstration of Topological-Order at 300K and a realization of topological-transport-regime
• Spin Transfer Torque Generated by the Topological Insulator Bi_2Se_3
• The quantum spin Hall effect and topological insulators
• Spintronics and Pseudospintronics in Graphene and Topological Insulators
• Surface quantized anomalous Hall current and magneto-electric effect in magnetically disordered topological insulators
• Emergent quantum confinement at topological insulator surfaces
• Electronic Structure of the Topological Insulator Bi2Se3 Using Angle-Resolved Photoemission Spectroscopy: Evidence for a Nearly Full Surface Spin Polarization
• Spin and Charge Transport on the Surface of a Topological Insulator
• Collective modes of a helical liquid
• Widespread spin polarization effects in photoemission from topological insulators
• Structural and electronic properties of highly doped topological insulator Bi2Se3 crystals
• Spin-polarized tunneling current through a thin film of topological insulator in a parallel magnetic field
• Giant magnetoresistance in the junction of two ferromagnets on the surface of diffusive topological insulators
• Bulk topological insulators as inborn spintronics detectors

Cited by in corpus (20)

• Electric-field control of spin-orbit torque in a magnetically doped topological insulator
• Room Temperature Electrical Detection of Spin Polarized Currents in Topological Insulators
• Electrical injection and detection of spin-polarized currents in topological insulator Bi2Te2Se
• Current-induced spin polarization in topological insulator-graphene heterostructures
• Tunneling Planar Hall Effect in Topological Insulators: Spin-Valves and Amplifiers
• Towards the understanding of the origin of charge-current-induced spin voltage signals in the topological insulator Bi${}_2$Se${}_3$
• The role of surface chemical reactivity in the stability of electronic nanodevices based on two-dimensional materials "beyond graphene" and topological insulators
• Effects of Defects and Dephasing on Charge and Spin Currents in Two-Dimensional Topological Insulators
• Hallmarks of non-trivial topology in Josephson junctions based on oxide nanochannels
• Controlling the Flow of Spin and Charge in Nanoscopic Topological Insulators
• Band tilt induced nonlinear Nernst effect in topological insulators: An efficient generation of high-performance spin polarization
• Epitaxial growth, magnetoresistance, and electronic band structure of GdSb magnetic semimetal films
• Opposite current-induced spin polarizations in bulk-metallic Bi2Se3 and bulk-insulating Bi2Te2Se topological insulator thin flakes
• Planar Josephson Hall effect in topological Josephson junctions
• Signature of pressure-induced topological phase transition in ZrTe${}_5$
• Large Magnetoresistance at Room Temperature in Ferromagnet/Topological Insulator Contacts
• Detection of current induced spin polarization in epitaxial Bi${}_2$Te${}_3$ thin film
• Electrical spin injection into graphene from a topological insulator in a van der Waals heterostructure
• Current Density of Majorana Bound States
• Structural and transport properties of 4f electron doped Y1-x(Dy)xPdBi topological semi-metallic thin films