Logo image
Back
Microscopic mechanisms of the bulk photovoltaic effect in sillenite single crystals
Dissertation

Microscopic mechanisms of the bulk photovoltaic effect in sillenite single crystals

Aaron M. Burger
Doctor of Philosophy (Ph.D.), Drexel University
20 Jun 2026
DOI:
https://doi.org/10.17918/00011453
pdf
Burger_Aaron_202625.26 MB
PDF Embargoed Access, Embargo ends: 30 Jun 2028

Abstract

Injection current Photogalvanic effect Quantum geometry Shift current Spin physics Quantum Physics Photonics
This dissertation presents an experimental study of the microscopic mechanisms governing the bulk photovoltaic effect (BPVE) in noncentrosymmetric sillenite single crystals of Bi₁₂SiO₂₀ and Bi₁₂GeO₂₀. While BPVE is described phenomenologically by macroscopic symmetry tensors, isolating the mechanisms that produce the measured photocurrent is complicated by their coexistence, sub-gap defect states, magnetic perturbations, and magneto-optical effects. Polarization modulated photocurrent detection resolves distinct contributions through their polarization and magnetic field dependence. Hall geometry measurements in Bi₁₂GeO₂₀ and Bi₁₂SiO₂₀ separate shift and ballistic current contributions, showing that both mechanisms coexist with comparable magnitudes in the measured sub-gap regime. Applying the same separation scheme to Bi₁₂SiO₂₀ under magnetic field establishes the conditions under which the separation remains quantitatively reliable, as the non-equivalence of the linear and circular carrier mobilities and the presence of magnetically induced photocurrent bound the spectral regime where the method applies. In the Voigt configuration, a symmetry forbidden odd-in-B longitudinal photocurrent is observed in Bi₁₂SiO₂₀ across the entire visible spectrum, persisting well below the band gap and exhibiting strong helicity selectivity. This response is not accounted for by the pristine point group 23 description and points to defect mediated symmetry lowering that unmasks latent quantum geometric responses encoded in the band structure of the space group I23. In the Faraday geometry, a phasor decomposition shows that most of the apparent magnetic field dependence of the linear photocurrent can be accounted for by magneto-optical polarization steering, and separates this contribution from intrinsic modification of the linear magnetophotovoltaic response.

Metrics

1 Record Views

Details

Logo image