Abstract
Negative Poisson's ratio (NPR) is a counterintuitive material elastic constant that can lead to many unusual auxetic properties. Here, using first-principles calculations, we report tunable negative Poisson's ratio in the out-of-plane direction in group-IV monochalcogenide monolayers (, Ge and , Se). SnSe, GeS, and SnS monolayers have intrinsic NPR ranging from to in armchair () tension, whereas GeSe monolayer possesses a much larger NPR of in zigzag () tension. Our analysis attributes the NPR effects to the relative position of and in the puckered structure and the smaller bending stiffness of bond angle. We further established the correlation between electronic structures of materials and their crystal structures. It allows us to fine tune GeSe structure via electron doping, leading to a reversible and continuous change of from up to 0.895. We also demonstrate the concept of strain engineering GeSe monolayer to switch its Poisson's ratio between two different values: 0.583 and . Our in-depth study provides not only fundamental knowledge but also practical routes for designing 2D smart materials with tunable negative Poisson's ratio, which are desirable for smart devices at small scale.
- Received 1 August 2018
- Revised 23 September 2018
DOI:https://doi.org/10.1103/PhysRevB.98.184104
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