Events

Chemical control of optoelectronic properties in 2D tungsten oxyhalides

Tunability in solid-state materials is essential for testing theory, discovering quantum phases, and enabling functionality. Layered van der Waals (vdW) semiconductors offer a unique platform, providing new degrees of freedom at the two-dimensional (2D) limit through exfoliation and external controls. In this presentation, I will demonstrate tunability of symmetry and electronic structure via halogen substitution in a family of layered vdW tungsten oxyhalides. Substituting the halogens in WO₂X₂ (X = I, Br, Cl) tunes the bandgap across a broad energy range and modifies the structural symmetry from centrosymmetric to noncentrosymmetric. By alloying WO₂I_2–yBr_y, the polar distortion and optical gap across the visible range are continuously tuned. Finally, I will discuss how chemical and photodoping modulate the SHG response in transition metal oxyhalides. These insights into halogen substitution and doping effects on symmetry and electronic structure lay the foundation for new tunable vdW semiconductors for optoelectronics and nonlinear optics.

Zoom Link: https://columbiauniversity.zoom.us/j/95900282572?pwd=PbmP4a8DzA4oj8j6Ovx78PS1HwV2Ta.1