Electronic properties and strain-induced optical response of monolayer CrS2

Problem. Two-dimensional transition metal dichalcogenides (TMDs) are promising candidates for
applications in next-generation optoelectronic and plasmonic devices due to their outstanding electronic and optical
properties. However, monolayer CrS2 remains understudied, and its strain-dependent optical response has not been
systematically investigated. Aim. To conduct a comprehensive first‑principles investigation of the effects of biaxial strain
on the optoelectronic properties of monolayer CrS2, in order to elucidate the microscopic mechanisms governing
strain‑induced optical responses and to provide a theoretical basis for the design of tunable optoelectronic and plasmonic
devices based on 2D materials. Methods. The study used density function theory (DFT) to analyze the electronic band
structure, dielectric function, and optical constant under different strain levels. Results. The results show that CrS2
possesses a direct bandgap of ~0.96 eV at the K-point, and the complex dielectric function ε(ω) exhibits distinct anisotropy
between in-plane and out-of-plane orientations. Furthermore, optical constants, including refractive index (n), extinction
coefficient (k), absorption coefficient (α), reflectivity (R), and energy loss function (L), are comprehensively analyzed.
Under biaxial strain ranging from −6 % to +6 %, a pronounced variation in the absorption and attenuation coefficients was
observed, with intensity increasing under tensile strain and decreasing under compressive strain, while reflectivity
remained low in the infrared–visible region, confirming optical behavior dominated by absorption. The energy loss
function revealed that plasmon resonances can be tuned by strain in the ultraviolet region. Conclusions. These findings
demonstrate that biaxial strain is an effective strategy for tuning the optical response of monolayer CrS2, highlighting its
potential in tunable optoelectronic and plasmonic applications.