Strain-tunable optoelectronics in a PdS₂ monolayer: the role of band nesting and carrier-phonon scattering

Strain engineering is a powerful strategy for tuning the optoelectronic properties of two-dimensional materials, yet the underlying mechanisms governing their strain response are often not fully elucidated. In this work, our first-principles calculations show that the penta-orthorhombic PdS₂ monolayer exhibits two key strain-tunable properties: a continuous redshift of its main optical absorption peak from ∼2.0 to ∼1.6 eV and an enhancement in carrier mobility, with a more than three-fold increase for electrons under 0-4% biaxial tensile strain. Subsequent analysis reveals that the tunable optical response originates from a robust band nesting feature between the highest valence and lowest conduction bands, which is preserved across the Brillouin zone under biaxial strain. For carrier transport, deformation potential theory predicts an increase in mobility with strain, strongly correlated with the reduction of carrier effective mass. Our first-principles calculations show a strain-induced monotonic decrease in carrier linewidths near the band edges, indicating suppressed carrier-phonon scattering and longer carrier lifetime as the origin of the mobility enhancement. Our work establishes a pathway for engineering optoelectronic responses in 2D semiconductors where strong band nesting governs the optical properties and paves the way for the rational design of continuously tunable flexible optoelectronic devices.