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Wednesday, October 9th 2019

1:25 pm:

2D semiconducting transition metal dichalcogenides (TMD) represent a unique class of 2D electronic system. The atomically-thin structure, just like graphene, eliminates finite thickness effects and facilitates gate-tunability. On the other hand, they hold promise for properties beyond graphene with a sizable band gap and strong spin-orbital coupling. In this talk, I will discuss correlated electronic states in WSe2 under a perpendicular magnetic field, probed through capacitance measurements. In monolayer WSe2, we observe fractional quantum Hall states with a unique sequence at odd-denominator fillings. In addition, an even-denominator state is observed which is expected to host non-Abelian statistics. In bilayer WSe2, the spin-valley locking, together with the valley misalignment in natural AB stacking, results in strongly suppressed interlayer tunneling and allows independent control of the individual layer population. We observe signatures consistent with interlayer exciton condensate when the two layers have matched orbital wavefunction. Interestingly, compared to other double layer systems with an intentional barrier, the natural bilayer has a smaller interlayer spacing and allows exciton condensate to be realized in high Landau levels, with different properties than the previously known version in the lowest Landau level .

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