Picosecond Valley Manipulation in Two-Dimensional In₂Se₃ via Ferroelectric Switching

Valleytronics, leveraging the valley degree of freedom in materials, holds promise for next-generation electronic and photonic devices. While most studies focus on degenerate valleys, the manipulation of nondegenerate valleys remains largely unexplored. Here, we demonstrate a novel approach for picosecond-scale valley manipulation in two-dimensional ferroelectric In₂Se₃ using <i>ab initio</i> quantum dynamics simulations. The conduction band of In₂Se₃ features nondegenerate Γ and M valleys, which can be selectively initialized via optical excitation. We show that ferroelectric switching drives intervalley electron transfer between these valleys, with the transfer efficiency modulated by temperature and switching speed. Our findings reveal that thermally excited phonons play a crucial role in facilitating intervalley coupling, enabling efficient valley manipulation. This work provides a new strategy for controlling valley degrees of freedom, advancing the field of valleytronics.