Inverted Chiral Response in Folded Anisotropic van der Waals Materials

In-plane anisotropic van der Waals (vdW) materials possess chirality-related degrees of freedom that can be identified by distinct vertical orientations. Despite their novel functionality, the realization of distinct vertical orientations in anisotropic vdW materials remains challenging. Herein, we propose a folding-based one-step approach for constructing structural differences. A representative in-plane anisotropic vdW material, rhenium disulfide (ReS₂), is electrochemically exfoliated and folded straight during the drop-casting process. While indistinguishable structural and electronic properties are obtained by atomic force microscopy and Kelvin probe force microscopy, optical characterizations such as photoluminescence and Raman spectroscopy reveal pronounced chiral phenomena. We confirm the opposite vertical orientation of the inverted region in folded ReS₂ flakes using polarized optical microscopy, angle-resolved photoluminescence, and Raman spectroscopy. Furthermore, chirality-dependent Raman spectra and photocurrent are observed, indicating that the inverted chiral response by folding the anisotropic vdW materials can be used for chirality-related optoelectronic applications.