Room Temperature Nonlocal Detection of Charge-Spin Interconversion in a Topological Insulator

Topological insulators (TIs) are emerging materials for next-generationlow-power nanoelectronic and spintronic device applications. TIs possessnon-trivial spin-momentum locking features in the topological surface states inaddition to the spin-Hall effect (SHE), and Rashba states due to highspin-orbit coupling (SOC) properties. These phenomena are vital for observingthe charge-spin conversion (CSC) processes for spin-based memory, logic andquantum technologies. Although CSC has been observed in TIs by potentiometricmeasurements, reliable nonlocal detection has so far been limited to cryogenictemperatures up to T = 15 K. Here, we report nonlocal detection of CSC and itsinverse effect in the TI compound Bi1.5Sb0.5Te1.7Se1.3 at room temperatureusing a van der Waals heterostructure with a graphene spin-valve device. Thelateral nonlocal device design with graphene allows observation of bothspin-switch and Hanle spin precession signals for generation, injection anddetection of spin currents by the TI. Detailed bias- and gate-dependentmeasurements in different geometries prove the robustness of the CSC effects inthe TI. These findings demonstrate the possibility of using topologicalmaterials to make all-electrical room-temperature spintronic devices.