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 ([Formula: see text]) violation leads to photoconduction. The [Formula: see text]symmetry 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 ([Formula: see text]10[Formula: see text]) 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 [Formula: see text]-symmetry breaking, and, therefore, the possibility of the photonic Aharonov–Bohm effect is expected in CuO thin films.

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“…This semiconductor state is in accordance with the theoretical result 57 and our experimental result. 58 In order to get the permittivity dispersion relation, we have used Norm conserving pseudopotentials and plotted [Fig. 3(c)].…”

“…The average thickness of the film (Z f ≃ 13, 22, and 27 nm for T5, T10, and T15, respectively) as estimated from the peak height distribution-normalized frequency plot (for details, see Ref. 58). Figure S2 in the supplementary material shows a schematic view of Atomic Force Microscopy (AFM) image (left) with 2D optical microscopy image of thin films (right).…”