Monolayer transition metal dichalcogenides are recently emerged 2D electronic systems with various novel properties, such as spin-valley locking, circular dichroism, valley Hall effects, Ising superconductivity. The reduced dimensionality and large effective masses further produce unconventional many-body interaction effects. Although recent hole transport measurements in WSe2 indicate strong interactions in the valence bands, many-body interaction effects, particularly in the conduction bands, remain elusive to date. Here, for the first time, we perform transport measurements up to a magnetic field of 29T to study the massive Dirac electron Landau levels (LL) in layer-polarized MoS2 samples with mobilities of 22000cm2/(V⋅s) at 1.5K and densities of ∼1012cm−2. With decreasing the density, we observe LL crossing induced valley ferrimagnet-to-ferromagnet transitions, as a result of the interaction enhancement of the g-factor from 5.64 to 21.82. Near integer ratios of Zeeman-to-cyclotron energies, we discover LL anticrossings due to the formation of quantum Hall Ising ferromagnets, the valley polarizations of which appear to be reversible by tuning the density or an in-plane magnetic field. Our results provide compelling evidence for many-body interaction effects in the conduction bands of monolayer MoS2 and establish a fertile ground for exploring strongly correlated phenomena of massive Dirac electrons.
@article{arxiv.1803.08007,
title = {Probing Landau levels of strongly interacting massive Dirac electrons in layer-polarized MoS$_2$},
author = {Jiangxiazi Lin and Tianyi Han and Benjamin A. Piot and Zefei Wu and Shuigang Xu and Gen Long and Liheng An and Patrick Ka Man Cheung and Peng-Peng Zheng and Paulina Plochocka and Duncan K. Maude and Fan Zhang and Ning Wang},
journal= {arXiv preprint arXiv:1803.08007},
year = {2019}
}