Valleytronics Meets Straintronics: Valley Fine Structure Engineering of 2D Transition Metal Dichalcogenides

Abstract 2D transition metal dichalcogenides (TMDs) have emerged as a novel class of semiconductors with promising applications in optoelectronics, owing to their rich and tunable valley fine structure, known as valleytronics. Strain engineering in TMDs presents opportunities to tailor their valley fine structures and band alignment, which greatly expands the potential to investigate their intrinsic properties and improve device performance, thus opening a new field of straintronics. In this review, recent advances in strain‐engineered 2D TMDs are summarized, with a focus on new phenomena and applications enabled by precision tuning of valley physics. The underlying mechanisms and connections are delineated between strain‐induced modifications to the valley fine structures based on intravalley, intervalley, and interlayer band alignment in single and heterostructure TMDs. These insights allow targeted strain control strategies to be devised for optimizing optoelectronic characteristics. This review provides perspectives and guidance on the future directions of valley‐straintronics and flexible 2D optoelectronics using TMDs, highlighting the substantial promise of valley‐strain engineering in TMDs for fundamental valley physics studies as well as practical device applications.