Abstract
Spin-momentum locking, which constrains spin orientation perpendicular to electron momentum, is attracting considerable interest for exploring various spin functionalities in semiconductors and topological materials. Efficient spin generation and spin detection have been demonstrated using the induced helical spin texture. Nevertheless, spin manipulation by spin-momentum locking remains a missing piece because, once bias voltage is applied to induce the current flow, the spin orientation must be locked by the electron momentum direction, thereby rendering spin phase control difficult. Herein, we demonstrate the spin-momentum locking-induced spin manipulation for ballistic electrons in a strong Rashba two-dimensional system. Electron spin rotates in a circular orbital motion for ballistically moving electrons, although spin orientation is locked towards the spin-orbit field because of the helical spin texture. This fact demonstrates spin manipulation by control of the electron orbital motion and reveals potential effects of the orbital degree of freedom on the spin phase for future spintronic and topological devices and for the processing of quantum information.
Highlights
The coupling of electron spin and orbital motion provides various spin functionalities: from spin-charge conversion to magnetization reversal[1,2,3,4,5,6]
The spin orientation takes the opposite direction to that of the spins generated in the emitter quantum point contacts (QPCs). (b) Spin orientations in momentum space based on equation (1)
Because the Rashba SO field depends on the direction of electron momentum, spin orientation is manipulated by modulating the electron orbital motion (Fig. 1a)
Summary
The coupling of electron spin and orbital motion provides various spin functionalities: from spin-charge conversion to magnetization reversal[1,2,3,4,5,6]. In a ballistic regime, where the electron trajectory plays a fundamentally important role, spin orientation can be rotated by modulating electron orbital motion because spin follows along the SO field direction under the ballistic orbital trajectory[17,18] To realize such spin manipulation in a ballistic regime, the long mean free path and strong SO interaction are required. Because the Rashba SO field depends on the direction of electron momentum, spin orientation is manipulated by modulating the electron orbital motion (Fig. 1a). This result demonstrates spin manipulation by spin-momentum locking in the ballistic regime. Because the frequency of spin precession under the SO field is faster than the cyclotron frequency, the adiabatic limit of spin rotation is satisfied, making it possible to lock the spin orientation in the direction of the SO field[17,18]
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