Magneto-chiral photocurrent in gyrotropic bulk single crystals

Aaron Burger ¹ Vladimir Fridkin ^2,3 Jonathan Spanier ^1,2,4,5

¹Department of Electrical and Computer Engineering, Drexel University, Philadelphia, PA, USA
²Department of Materials Science and Engineering, Drexel University, Philadelphia, PA, USA
³Shubnikov Institute of Crystallography, Shubnikov Institute of Crystallography, Moscow, Russia
⁴Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, PA, USA
⁵Department of Physics, Drexel University, Philadelphia, PA, USA

Longitudinal circular photocurrent in Bi₁₂SiO₂₀ single crystals responds unexpectedly to external applied magnetic field in a Voigt configuration. The measured effect seems to defy phenomenological description for bulk photovoltaic effect in magnetic field. Magnetic field response across the visible spectrum, as well as for above band gap E_g ≈ 3.2 eV illumination all reveal much greater sensitivity to magnetic field for circularly polarized light when compared with linearly polarized light. While Faraday effect is well documented in Bi₁₂SiO₂₀, we present data that extend the wavelength and temperature range of existing magneto optic data. Peaks in the longitudinal (nonmagnetic) circular current with λ≈525 nm correspond with temperature independence of Verdet coefficient as measured in Bi₁₂SiO₂₀. The anomalous non-Hall response to magnetic field suggests that the observed magnetic field dependent behavior of the current results from magneto induced changes to the generation rate of spin polarized carriers excited from paramagnetic impurity centers. Work supported by the NSF and the U.S. Army Research Office.