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arXiv · 2608.03049

Hidden Quantum Geometry in Bilayer Exciton Condensates

Xuzhe Ying·Benjamin T. Zhou
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Abstract

When an electron-doped layer is stacked with a hole-doped layer with approximately equal carrier density, inter-layer Coulomb interaction turns the bilayer system into an exciton condensate (EC). In this Letter, we reveal a fundamental property of bilayer ECs: the excitonic order gives rise to nontrivial hidden quantum geometric effects in the correlated electron-hole bands, even when the non-interacting bands are trivial. Such peculiar EC-driven quantum geometry manifests itself in a characteristic out-of-plane polarization response upon applying an in-plane AC electric field to the bilayer EC system. In particular, the second-order response exhibits a characteristic inverse square scaling with the bilayer EC order parameter. Our finding reveals a fundamental hidden Berry phase effect driven by electron-hole correlations, and establishes bilayer EC as a promising platform for rich nonlinear physics.

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Xuzhe Ying, Benjamin T. Zhou. 2026-08-04. Hidden Quantum Geometry in Bilayer Exciton Condensates. https://arxiv.org/abs/2608.03049

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