Ductile Dirac-like Semimetal SrSn 3 for Flexible Optoelectronics.

The development of mechanically compliant quantum materials with nontrivial electronic states and strong light-matter interactions is an important frontier for flexible optoelectronics and strain-engineered devices. In this research, we systematically investigate the structural, elastic, electronic, and optical properties of cubic intermetallic SrSn3, using first-principles density functional theory. Our calculations establish the dynamical stability of SrSn3 and reveal a semimetallic electronic structure featuring Dirac-like linear band crossings near the Fermi level, accompanied by a remarkably soft mechanical response that contrasts strongly with the comparatively brittle CaSn3. SrSn3 exhibits an exceptionally low Pugh's ratio (G/B = 0.19), a low Vickers hardness (Hᵥ = 0.54 GPa), and nearly isotropic elastic behavior, indicating a pronounced ductile tendency and strong mechanical compliance. The electronic structure features robust linear band crossings along the Γ-X and R-X high-symmetry directions, with substantial contributions from the hybridization of Sr-3d and Sn-5p states. These electronic characteristics are accompanied by a pronounced broadband optical response, including an infrared plasmon resonance, high optical conductivity, and strong interband absorption exceeding 105 cm-1 across broad regions of the visible-to-ultraviolet spectrum. Furthermore, strain-dependent calculations demonstrate that the electronic states and optical characteristics, including absorption edges and plasmonic features, can be systematically modulated within the investigated strain range of -4% to +4%. The combination of Dirac-like semimetallic behavior, exceptional mechanical compliance, and strain-tunable optical functionality highlights SrSn3 as a promising platform for flexible photodetectors, wearable optoelectronics, and mechanically deformable quantum-device architectures.