Semiconducting transition-metal dichalcogenides (TMDs) exhibit high mobility,
strong spin-orbit coupling, and large effective masses, which simultaneously
leads to a rich wealth of Landau quantizations and inherently strong electronic
interactions. However, in spite of their extensively explored Landau levels
(LL) structure, probing electron correlations in the fractionally filled LL
regime has not been possible due to the difficulty of reaching the quantum
limit. Here, we report evidence for fractional quantum Hall (FQH) states at
filling fractions 4/5 and 2/5 in the lowest LL of bilayer MoS2, manifested
in fractionally quantized transverse conductance plateaus accompanied by
longitudinal resistance minima. We further show that the observed FQH states
sensitively depend on the dielectric and gate screening of the Coulomb
interactions. Our findings establish a new FQH experimental platform which are
a scarce resource: an intrinsic semiconducting high mobility electron gas,
whose electronic interactions in the FQH regime are in principle tunable by
Coulomb-screening engineering, and as such, could be the missing link between
atomically thin graphene and semiconducting quantum wells.Comment: 10 pages, 4 figure