Structural and electronic anisotropy, negative Poisson’s ratio, strain-sensitive Dirac-like cone in monolayer α-CSe: Tailoring electronic properties

Abstract Using density functional theory (DFT), a designed isoelectronic counterpart of phosphorene, black-phosphorus-analogous monolayer CSe (α-CSe) was confirmed to be stable. α-CSe displays apparently anisotropic behaviors of in-plane mechanics through calculating ideal tensile strength and critical strain, which thus causes anisotropic response to in-plane strains in its electronic and transport properties. It was found that the monolayer α-CSe can endure an ultimate stress of 4.008 N/m along armchair direction at e x = 0.28 , and 10.96 N/m along zigzag direction at e y = 0.22 . Intriguingly, the strain praxis of α-CSe under zigzag deformation highlights a negative out-of-plane Poisson’s ratio of −0.76 rooted in its puckered structure. Direct-to-indirect bandgap transitions and reverse transitions occurred alternatively under uniaxial and biaxial strains, which in essence issued in drastic variation of effective mass in k-place. Thus, the prior transport direction of carriers can be feasibly tuned by imposing biaxial strain. However, the preferred armchair transport direction is irrespective of strain size and present good mechanical stability, under the uniaxial strain. The anisotropic Dirac-like dispersions in α-CSe were identified at appropriate strain value, which unveiled the ballistic conduction along Γ-Y. Our numerical results offered meritorious information of puckered sheets by insight into α-CSe, and revealed the prospects of α-CSe in nano-devices applications.