International Journal of Physics | Vol. 2, No. 1, January 2011 | pp. 1–9
DOI: 10.46882/2011/IJP/000013
Article Type: Original Research Paper
Title: Electronic and Topological Properties of Two-Dimensional Transition Metal Dichalcogenide Monolayers under Asymmetric Strain
Names of Authors: O. K. Oyewande¹, T. H. Kim²
Authors’ Affiliations: ¹Department of Physics, University of Ibadan, Ibadan, Nigeria; ²Department of Physics and Astronomy, Seoul National University, Seoul, South Korea
Abstract: Monolayers of transition metal dichalcogenides (TMDs) exhibit unique electronic and optical features that are missing in their bulk counterparts, making them promising candidates for flexible nanoelectronics and valleytronics. This paper examines the modulation of electronic band structures and topological invariants in molybdenum disulfide (MoS₂) and tungsten diselenide (WSe₂) monolayers subjected to asymmetric uniaxial and biaxial tensile strains. The computations were executed using first-principles density functional theory (DFT) with the inclusion of spin-orbit coupling (SOC) effects. Our findings reveal that pristine monolayers exhibit a direct bandgap at the K point, which transitions to an indirect bandgap under a critical uniaxial strain of 2.5% for MoS₂ and 1.8% for WSe₂. Increasing the biaxial tensile strain beyond 6.5% induces a semiconductor-to-metal phase transition, driven by the differential orbital shifts of the transition metal d-states and chalcogen p-states. Furthermore, applying an asymmetric strain configuration breaks the local inversion symmetry, leading to a spin-splitting energy of up to 185 meV at the valence band maxima. This strain-engineered splitting enhances the valley-selective optical absorption coefficient, demonstrating a viable pathway for controlling spin and valley indices in mechanical strain-modulated nanoelectronic devices.
Keywords: Transition metal dichalcogenides; Density functional theory; Strain engineering; Electronic bandgap; Spin-orbit coupling; Semiconductor-to-metal transition; Monolayer MoS₂; Valleytronics.
Manuscript Timeline: Received: October 14, 2010; Revised: November 25, 2010; Accepted: December 16, 2010; Published: January 08, 2011.
Citation: Oyewande, O. K., & Kim, T. H. (2011). Electronic and Topological Properties of Two-Dimensional Transition Metal Dichalcogenide Monolayers under Asymmetric Strain. International Journal of Physics, 2(1), 1–9.
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