Indirect-direct band gap transition driven by strain in semiconducting Cu2Se monolayer

Cu2Se monolayer (ML) synthesized experimentally is a member of transition metal chalcogenides materials, which has attracted significant attention due to its diversity and unique properties. However, the feature of an indirect band gap of Cu2Se ML in the low-temperature phase limits its' application in electronics devices. Our study results based on the first principle calculations show that indirect-direct band gap transitions can occur in Cu2Se ML under appropriate uniaxial or biaxial strains. The band gap of Cu2Se ML is controllable due to the different responses of the edge-states near the Fermi level to the strain. The phonon dispersion suggests that the semiconducting Cu2Se ML can maintain dynamic stability in a wide range of strains. With the tunable electronic structure, semiconducting Cu2Se ML would become a promising candidate for electronic devices.