Two-component exciton condensates in an electron-hole bilayer.
basic_science · Level V
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- Record sourced from PubMed, PMID 42271053.
- Also identified by DOI 10.1038/s41586-026-10636-y.
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Abstract
Macroscopic quantum coherence emerges when bosons condense into a Bose-Einstein condensate (BEC)<sup>1-5</sup>. Excitons are a long-sought solid-state route to high-temperature BECs with strong interactions, electrical tunability and potentially multicomponent spinor order, but conclusive evidence for equilibrium condensation has remained elusive. Here we report evidence for two-component exciton BECs in MoSe<sub>2</sub>/hBN/WSe<sub>2</sub> electron-hole bilayers<sup>6-9</sup> by probing the spin-valley susceptibility of constituent electrons and holes. This heterostructure hosts equilibrium exciton fluids with four spin-valley flavours. Magneto-optical spectroscopy in a dilution refrigerator reveals three exciton condensate phases with distinct flavour polarizations. At zero magnetic field, the many-body ground state is a coherent superposition of two condensed intravalley exciton flavours. Under a magnetic field, the intravalley exciton condensate first switches to a two-component intervalley condensate through a first-order quantum phase transition at a weak critical field and then turns into a fully polarized single-component condensate at high fields. The condensate signatures form a dome in density-temperature space, persisting up to approximately 1.8 K. Our results establish van der Waals electron-hole bilayers as a versatile platform for strongly interacting, multicomponent exciton BECs.