Abstract
The appearance of topologically protected spin-momentum locked surface states in topological insulators gives rise to robust room temperature spin currents making them ideal candidates for the realization of spintronic devices. New methods are needed to access and manipulate such currents with timescales that are compatible with modern electronics. Here we reveal that an optically induced long-lived (~10 ns), spin-polarized surface state excitation in topological insulators can be easily tuned in both magnitude and duration. Time-resolved angle-resolved photoemission spectroscopy, together with a quantitative model, reveals the ideal conditions for a surface photovoltage in two different topological insulators. Our model predicts that the reported effects are an intrinsic property of topological insulators, as long as the chemical potential falls within the band gap. This work demonstrates that persistent excited topological surface states are photon-accessible and easily tuned in both magnitude and duration, merging photonics- and spintronics-based devices in the same material.
Highlights
The surface photovoltage effect (SPV) in conventional semiconductors is a well-known phenomenon used extensibly for semiconductor characterization across a wide range of material properties[1,2]
In this study we reveal that when the prototypical topological insulators Bi2Se3 and Bi2Te3 are doped into the bulk band gap and are pumped with 800 nm light, a strong, long-lived (~10 ns) and tunable SPV effect develops
We argue that the ideal situation to realize such an effect is when the chemical potential falls within the band gap, due to the intricate relation between the existence of a topological surface state, the band bending of the insulating bulk and photoexcited hole trapping in the bulk
Summary
The surface photovoltage effect (SPV) in conventional semiconductors is a well-known phenomenon used extensibly for semiconductor characterization across a wide range of material properties[1,2]. In this study we reveal that when the prototypical topological insulators Bi2Se3 and Bi2Te3 are doped into the bulk band gap and are pumped with 800 nm light, a strong, long-lived (~10 ns) and tunable SPV effect develops.
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