Probing the Strain Direction‐Dependent Nonmonotonic Optical Bandgap Modulation of Layered Violet Phosphorus

Abstract Recent theoretical investigations have well‐predicted strain‐induced nonmonotonic optical band gap variations in low‐dimensional materials. However, few two‐dimensional (2D) materials are experimentally confirmed to exhibit nonmonotonic optical band gap variation under varying strain. Here, a strain‐induced nonmonotonic optical bandgap variation in violet phosphorus (VP) nanosheets is observed, as evidenced by photoluminescence spectroscopy, which is reported in a few other 2D materials in knowledge. The optical bandgap variations are characterized to show the modulation rates of 41 and −24 meV/% with compression and tensile strains, respectively. Remarkably, first‐principle calculations predict and clarify the nonmonotonic modulation accurately, highlighting its relationship with the strain direction‐dependent asymmetric distribution of conduction band minimum wavefunctions, demonstrating that this unique nonmonotonic optical bandgap modulation is determined by the distinctive crystal structure of VP. This work provides a deep insight into the design of 2D materials toward optoelectronic and photoelectrochemical applications via strain engineering.