Phys.org June 14, 2023
A typical frustrated system is correlated bosons on moat bands, which could host topological orders with long-range quantum entanglement. However, the realization of moat-band physics is still challenging. Researchers at UMass, Amherst explored moat-band phenomena in shallowly inverted InAs/GaSb quantum wells, where they observed an unconventional time-reversal-symmetry breaking excitonic ground state under imbalanced electron and hole densities. They found a large bulk gap encompassing a broad range of density imbalances at zero magnetic field (B), accompanied by edge channels that resemble helical transport. Under an increasing perpendicular B, the bulk gap persisted, and an anomalous plateau of Hall signals appeared demonstrating an evolution from helical-like to chiral-like edge transport with a Hall conductance. Theoretically they showed that strong frustration from density imbalance leads to a moat band for excitons resulting in a time-reversal-symmetry breaking excitonic topological order, which explained their experimental observations. According to the researchers their work opens a new direction for research on topological and correlated bosonic systems in solid states beyond the framework of symmetry-protected topological phases… read more. TECHNICAL ARTICLEÂ
Rendering of the moat band, which frustrates particles and leads to the chiral bose-liquid state. Credit: Tigran Sedrakyan, UMass, Amherst.