Origin of contrasting trends of intrinsic electron mobility with tensile strain in hexagonal <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>MoS</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math> and triangular <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>PdSe</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>
Gege Du, Chunhui Li, Long Cheng
Abstract
Strain engineering is an effective method to extend the properties of two-dimensional (2D) materials. In this paper, we theoretically studied the electron mobility of 2D hexagonal (H) ${\mathrm{MoS}}_{2}$ and triangular (T) ${\mathrm{PdSe}}_{2}$ under different strains. We observe contrary trends of the electron transport with strain. Our study shows it inherently comes from the contrary response of chemical bonding to strain. The covalency of both $\mathrm{H}\text{\ensuremath{-}}\mathrm{Mo}{\mathrm{S}}_{2}$ and $\mathrm{T}\text{\ensuremath{-}}\mathrm{PdS}{\mathrm{e}}_{2}$ decreases with increasing strain due to the elongated bond length. The ionicity of $\mathrm{H}\text{\ensuremath{-}}\mathrm{Mo}{\mathrm{S}}_{2}$ is also decreased, resulting in decreased electron-phonon coupling strength. On the contrary, the ionicity of $\mathrm{T}\text{\ensuremath{-}}\mathrm{PdS}{\mathrm{e}}_{2}$ is increased, which overwhelms the decrease of the covalency, resulting in enhanced electron-phonon coupling strength. Our work not only uncovers the underlying physics governing the contrary trends of electron mobility with strain in hexagonal and triangular $M{X}_{2}$, but also offers a paradigm analysis methodology that is applicable to other research areas.