Ferroelectric control optical absorption in quasi-1D chalcogenide BaTiS3

Abstract

Low-dimensional van der Waals (vdW) materials can develop sizeable ferroelectric polarization and intriguing optical behaviors at atomic thickness, attracting widespread attention due to their potential applications in low-power memories, high-efficient photovoltaics, and promising optoelectronic devices. 1D vdW materials have been discovered to present strong anisotropic structural and electronic behaviors that enrich the landscape of ferroelectric and optical playgrounds to unlock new functionalities. In this work, we investigated the quasi-1D material BaTiS3, which exhibits robust in-plane ferroelectricity at monolayer thickness, driven by a soft polar mode displacement. Moreover, the optical absorption in monolayer BaTiS3 exhibits strong anisotropy, with higher intensity along the chain direction than perpendicular to it. In addition, the optical absorption along the chain direction is highly dictated by the ferroelectric functionality, which exhibits about threefold enhancement in intensity and 1 eV shift in frequency. The tunable optical absorption is attributed to the modulation of orbital symmetry and band dispersion in the top valence and bottom conduction bands, governed by the ferroelectric mode. Our study on ferroelectric and optical properties in 1D ferroelectric BaTiS3 offers a new affordable candidate for designing advanced photodetectors, photovoltaics, and hyperbolic materials.