Strain-engineered tunable negative Poisson's ratio and anisotropic mechanics in tellurene

Two-dimensional (2D) auxetic materials exhibiting negative Poisson's ratio (NPR) have garnered significant attention for their exceptional mechanical properties, which enable groundbreaking applications in flexible electronics and nanoelectromechanical systems. While conventional auxetic behavior in graphene-like honeycomb structures relies on sp2 hybridization, this study reveals an unconventional NPR mechanism in strain-engineered tellurene that surpasses classical elasticity limits (−1 to 0.5). Through first-principles calculations, we demonstrate that 22% tensile strain along the zigzag direction induces an ultrahigh NPR of −1.67 in tellurene—a value exceeding all reported 2D materials to date. This phenomenon arises from a synergistic interplay of structural and electronic transitions: (1) bond-angle expansion and (2) buckling-height reduction under strain, which collectively drive the anomalous auxetic response. Furthermore, our analysis uncovers a strain-mediated phase transition that fundamentally alters both the geometric configuration and electronic band structure of tellurene. The findings not only establish tellurene as a paradigm-shifting auxetic material but also propose a universal design principle for strain-tunable anisotropic mechanics in non-honeycomb 2D systems.