Anisotropic photoconduction in ultrathin CuO: A nonreciprocal system?

Abstract

With the recent global surge in the research on perovskite halides, CuO is one of the binary oxides, which gets attention as a hole transport material. In centrosymmetric CuO, parity-time (PT) violation leads to photoconduction. The PTsymmetry can be preserved if the system were non-reciprocal. Thus, in the current work, we fabricated an ultra-thin film of CuO using pulsed laser deposition and observed anisotropic photoconduction. The semiconductor parameters estimated from the photoresponse suggest that the relative value of free charge carrier density is neither altered significantly with thickness reduction nor with light exposure as it is quite low (∼10−7) suggesting high trap (deep) density. Further, anisotropic photocurrent in the absence of an electric field suggests the alteration in electromagnetic potential due to the existence of self-biasing and structural asymmetry. The application of Gauge field variance on 2D photonic metasurface reveals the non-chiral nature. It is suggesting T-symmetry breaking, and, therefore, the possibility of the photonic Aharonov–Bohm effect is expected in CuO thin films.