A research team from Sookmyung Women's University's Department of Intelligent Electronic Systems has revealed a new physical mechanism that explains the observation principle of 'interlayer excitons' formed in two-dimensional semiconductors through the application of electric fields. Interlayer excitons, which are created when electrons and holes exist in different layers of a two-dimensional semiconductor, are essential for future optoelectronic devices and quantum information technologies. However, their optical interaction is weak, making them difficult to observe optically due to their separation across layers.

The research team conducted precise measurements of the optical spectrum while applying an electric field to a two-layer structure of tungsten diselenide (WSe2), a two-dimensional semiconductor material. They discovered that the typically weak signals from interlayer excitons became stronger with increasing electric field strength. Previous studies had explained this phenomenon through the hybridization of two types of exciton states, but the team determined that this explanation was insufficient to account for their experimental results.

By combining density functional theory (DFT) calculations and exciton modeling, the research team proposed a new mechanism that involves the movement of the wave function of holes from one layer to another in an applied electric field, forming quantum superposition states with interlayer excitons. This process amplifies the interaction with light, transforming the originally dark interlayer excitons into a brighter state. The team’s calculations suggested that the mechanism of hole movement accounts for the increase in brightness of interlayer excitons, diminishing the previously regarded significance of exciton hybridization in this context. This study marks an important step in understanding the optical properties of interlayer excitons in two-dimensional semiconductors.