First-principles calculations of the optoelectronic properties of Cr-based quasi-one-dimensional A2Cr3As3 (A = K, Rb, or Cs) superconductors

The quasi-one-dimensional chromium-based superconductors A₂Cr₃As₃ (A = K, Rb, Cs) have attracted considerable attention due to their unconventional superconductivity, strong electronic correlations, and noncentrosymmetric crystal structure. Experimental studies—including measurements of penetration depth, NMR, μSR, and specific heat—consistently indicate nodal superconductivity and pronounced spin fluctuations in these materials, making them promising systems for exploring topological superconducting phases and low-dimensional quantum physics. Despite extensive experimental progress, several fundamental physical characteristics, including their electronic and optical response, remain insufficiently understood. In this work, we conduct a first-principles investigation of the structural, electronic, and optical properties of A₂Cr₃As₃ using Density Functional Theory (DFT) within the CASTEP framework. The generalized gradient approximation of Perdew–Burke–Ernzerhof is employed alongside ultrasoft Vanderbilt pseudopotentials to model electron–ion interactions accurately. Detailed analyses of lattice parameters, electronic density of states, band structure, dielectric response, and optical conductivity are presented. Our results provide new insight into the electronic behavior and optical characteristics across the K–Rb–Cs series. These findings not only fill critical gaps in the current understanding of Cr-based arsenide superconductors but also offer valuable guidance for future experimental and theoretical research in low-dimensional and topological superconductivity.