title: Density-functional tight-binding simulations of curvature-controlled layer decoupling and band-gap tuning in bilayer MoS2.
abstract: Monolayer transition-metal dichalcogenides (TMDCs) display valley-selective circular dichroism due to the presence of time-reversal symmetry and the absence of inversion symmetry, making them promising candidates for valleytronics. In contrast, in bilayer TMDCs both symmetries are present and these desirable valley-selective properties are lost. Here, by using density-functional tight-binding electronic structure simulations and revised periodic boundary conditions, we show that bending of bilayer MoS2 sheets breaks band degeneracies and localizes states on separate layers due to bending-induced strain gradients across the sheets. We propose a strategy for employing bending deformations in bilayer TMDCs as a simple yet effective means of dynamically and reversibly tuning their band gaps while simultaneously tuning valley-selective physics.
authors.affiliation: NanoScience Center, Department of Physics, University of Jyväskylä, 40014 Jyväskylä, Finland.
authors.forename: Pekka
authors.initials: P
authors.lastname: Koskinen
authors.affiliation: Department of Mechanical and Industrial Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA.
authors.forename: Ioanna
authors.initials: I
authors.lastname: Fampiou
authors.affiliation: Department of Mechanical and Industrial Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA.
authors.forename: Ashwin
authors.initials: A
authors.lastname: Ramasubramaniam