Straintronics with single-layer MoS2: A quantum Monte Carlo study

Abstract

Using state-of-the-art quantum Monte Carlo (QMC) methods, we study straintronic properties of a single MoS2 monolayer. 2D MoS2 is a quintessential straintronic material for which many experiments have been performed. First, we determine the equilibrium atomic structure which is not known experimentally and is strictly needed to correctly determine the straintronic properties. That enables us to precisely analyze the quasiparticle band gaps for any applied biaxial strain, which we describe by a bivariate paraboloid function of lattice constant and internal structural parameter. Using the fixed-node QMC calculations fitted by analytical formulas, we localize the following excited state crossings between the direct, K→K, and indirect Γ→X and K→K/2 excitations. Based on this highly accurate many-body treatment, we predict a gauge factor of 136 meV/% for the K→K transition and a fairly narrow window of ≈2.8% from compressive to mildly tensile strains, accounting for only ≈0.3 eV band gap change maintaining the direct character of the gap. Consequently, we suggest that, compared to other 2D materials, such as phosphorene, there is only a limited straintronic tuneability in this material often studied for its straintronic properties. QMC results are compared to results of standard DFT modeling, which reveal insights into the corresponding inaccuracies and therefore open a window for educated use of rapid DFT approaches.