Large Unsaturated Magnetoresistance in Gated MoS2 Flakes

Abstract

Transition metal dichalcogenides (TMD) are a fertile playground to study the interactions between charge carriers and external magnetic fields. Van der Waals interlayer interactions enable the investigation of magnetotransport as a function of the different numbers of TMD layers. Here, we demonstrate unsaturated large magnetoresistance (MR) in MoS2 crystals by using a field-effect transistor geometry to tune charge carrier density. Our work shows that the device can be operated in a given regime that allows reaching a maximum MR of 680% at 1.8 K without any sign of saturation. The device exhibits a higher sensitivity to magnetic fields when operating in the subthreshold regime than in its on-state. Our work suggests that this effect stems from a change in the energy of the conducting states as observed by monitoring the threshold voltage shift. Notably, the magnitude of such a shift strongly decreases with temperature and number of layers. By means of Density Functional Theory calculations, we confirm that the origin of such a large MR is not the Lorentz force affecting band-like transport, but rather, an interaction that affects the electronic properties of mid-gap states in MoS2 that are dominating the charge transport at low temperature. This work demonstrates that controlling the charge density in the channel and the transport mechanism leads to engineering of the magnetic sensitivity in 2D materials.