Direct evidence of phase coherence in exciton condensates

Establish direct experimental evidence for phase coherence in exciton condensates formed in solid-state platforms by identifying and measuring an observable that unambiguously demonstrates coherent electron–hole pairing, rather than relying on indirect transport signatures.

Background

The paper discusses exciton and dipole condensates, highlighting that charge-neutral composite bosons such as excitons are insensitive to ordinary vector gauge fields. In solid-state bilayer systems, signatures like Coulomb drag suggest correlated electron–hole dynamics, but these transport measurements are often indirect and can be affected by disorder, leaving phase coherence difficult to confirm conclusively.

To address this challenge, the authors propose a highly tunable ultracold-atom platform with synthetic rank-2 electric fields that can imprint phase twists on dipole condensates and generate dipolar supercurrents obeying a Josephson relation, offering a route to directly probe phase coherence. Nonetheless, in solids, obtaining unambiguous, direct evidence for phase coherence in exciton condensates remains an outstanding problem.