Intrinsic electron-hole separation and tunable valley polarization in strain-engineered MXene Cr 2 COCl

Abstract Valleytronics, as an emerging electronic degree of freedom, holds significant potential in low-power devices. However, achieving valley polarization and efficient electron-hole separation remains a challenge. Through first-principles calculations, this study proposes the two-dimensional MXene material Cr 2 COCl as an ideal platform for valleytronics. The results indicate that Cr 2 COCl is a ferromagnetic semiconductor with significant valley polarization properties. Its unique layer-resolved orbital contributions enable intrinsic electron-hole separation, thereby effectively suppressing carrier recombination. Biaxial strain linearly modulates valley splitting and Berry curvature, enabling reversible control of the anomalous valley Hall effect (AVHE). When tensile strain is applied, the system undergoes a topological phase transition, producing a non-zero Chern number ( C = 1) and chiral edge states. These findings confirm that Cr 2 COCl can be used to regulate carriers, adjust valley polarization, and generate topological states through strain engineering, providing a theoretical basis for designing high-performance, low-power valleytronic devices.