Strain-Tunable Opto-electronics in PdS$_2$ Monolayer: the Role of Band Nesting and Carrier-Phonon Scattering

TL;DR

This study demonstrates how biaxial strain can continuously tune the optical absorption and significantly enhance carrier mobility in PdS$_2$ monolayers by leveraging band nesting and reduced carrier-phonon scattering, enabling flexible optoelectronic device design.

Contribution

It reveals the mechanisms behind strain-induced optical and electronic property tuning in PdS$_2$, highlighting the role of band nesting and phonon scattering reduction, which was not previously understood.

Findings

Optical absorption peak redshifts from 2.0 to 1.6 eV under strain.

Carrier mobility increases over threefold with 0-4% biaxial tensile strain.

Carrier-phonon scattering is suppressed, extending carrier lifetime.

Abstract

Strain engineering is a powerful strategy for tuning the optoelectronic properties in two-dimensional materials, yet the underlying mechanisms governing their strain response are often not fully elucidated. In this work, our first-principle calculations show that the penta-orthorhombic PdS$_2$ monolayer exhibits two key strain-tunable properties: a continuous redshift of its main optical absorption peak from $\sim$2.0 to $\sim$1.6~eV and enhancement in carrier mobility, with a more than threefold increase for electron 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 the carrier transport, deformation potential theory predicts mobility increasing with strain, strongly correlating 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 the optoelectronic response 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.