The optical selection rule states that opposite parity between the valence and conduction bands is required for optical absorption to occur. However, monolayer hexagonal transition metal dichalcogenides (h-TMDs) such as MoS2 exhibit pronounced optical absorption despite their nominally dipole-forbidden d-d transitions. In this Letter, we elucidate a parity inversion mechanism through which obstruction-driven band inversion promotes dipole-allowed optical transitions near the band edge in monolayer h-TMDs. By comparing trivial and obstructed atomic limit phases, we show that intersite interactions between hybridized d orbitals induce parity inversion. Our results provide a novel approach to tuning optical properties through parity control, bridging the gap between topology and light-matter interaction.
@article{arxiv.2510.01575,
title = {Obstruction-Driven Parity Inversion for Enhanced Optical Absorption in Hexagonal Transition Metal Dichalcogenides},
author = {Seungil Baek and Jun Jung and Yong-Hyun Kim},
journal= {arXiv preprint arXiv:2510.01575},
year = {2025}
}