Crossover between strongly coupled and weakly coupled exciton superfluids

In fermionic systems, superconductivity and superfluidity occur through the condensation of fermion pairs. The nature of this condensate can be tuned by varying the pairing strength, which is challenging in electronic systems. We studied graphene double layers separated by an atomically thin insulat...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 2022-01, Vol.375 (6577), p.205-209
Main Authors: Liu, Xiaomeng, Li, J I A, Watanabe, Kenji, Taniguchi, Takashi, Hone, James, Halperin, Bertrand I, Kim, Philip, Dean, Cory R
Format: Article
Language:English
Subjects:
Bosons
Condensates
Condensation
Counterflow
Electronic systems
Excitons
Fermi gases
Fermions
Graphene
Magnetic fields
Magnetism
Phase diagrams
Science & Technology - Other Topics
Separation
Superconductivity
Superfluidity
Temperature dependence
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Summary:In fermionic systems, superconductivity and superfluidity occur through the condensation of fermion pairs. The nature of this condensate can be tuned by varying the pairing strength, which is challenging in electronic systems. We studied graphene double layers separated by an atomically thin insulator. Under applied magnetic field, electrons and holes couple across the barrier to form bound magneto-excitons whose pairing strength can be continuously tuned by varying the effective layer separation. Using temperature-dependent Coulomb drag and counterflow current measurements, we were able to tune the magneto-exciton condensate through the entire phase diagram from weak to strong coupling. Our results establish magneto-exciton condensates in graphene as a model platform to study the crossover between two bosonic quantum condensate phases in a solid-state system.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.abg1110