Helicity dependent photovoltaic effect in Bi2Se3 under normal incident light

TL;DR

This study demonstrates a helicity-dependent photovoltaic effect in Bi2Se3 topological insulators under normal incident light, revealing out-of-plane spin components and potential for spin current control in optoelectronic devices.

Contribution

It uncovers the helicity dependence of photovoltaic effects in Bi2Se3 under normal light, linked to surface state spin textures and electrostatic potential fluctuations.

Findings

Helicity dependence observed in photovoltaic response.

Out-of-plane spin components due to hexagonal warping.

Surface electrostatic fluctuations enable the effect.

Abstract

Topological insulators (TIs) form a new class of materials with insulating bulk and surface conduction ensured by topologically protected surface states (TPSS). We investigate the impact of the helicity of a normally incident laser beam on the photovoltaic effect in the TI Bi2Se3. The observation of a helicity dependent photovoltaic effect for normally incident light indicates the presence of out-of-plane spin components for some TPSSs due to the hexagonal warping. In addition, fluctuations in the electrostatic potential at the surface locally break the rotational symmetry of the film allowing the helicity dependent photovoltaic effect. Our result suggests that engineering local electrostatic potentials in Bi2Se3 would allow the control of optically generated spin currents, which may be useful for applications in spin-optoelectronics.