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R. G. Herb Condensed Matter Seminar
Tunable Excitonic Ground States in Double Layer Graphene
Date: Thursday, January 23rd
Time: 10:00 am
Place: 5310 Chamberlin
Speaker: Yihang Zeng, Columbia University
Abstract: Two-component quantum Hall systems, such as double layer graphene (DLG) separated by a tunnel barrier, have been demonstrated to host ground states of indirect interlayer exciton when the lowest Landau level (LL) in each layer is half filled. Upon decreasing the temperature, the system will condense into a macroscopically ordered state with quasi long-range phase coherence, termed exciton condensate, a superfluid of exciton. We realized the crossover between exciton condensate with strong coupling and weak coupling by changing the exciton density. Upon unbalancing the density in each layer, we observe a sharp transition from an exciton superfluid to an exciton insulator, insulating in both charge transport and exciton transport measurement, which is interpreted as a Wigner crystal of exciton pinned by disorder. With tunable Bohr radius and exciton-exciton distance, we for the first time show the entire phase diagram of the excitonic ground states in the lowest LL in DLG.
Host: Alex Levchenko
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