Researchers Link Path Symmetry to Interaction-Driven Quantum Transport

Researchers have discovered that the destruction of Aharonov-Bohm (AB) caging is an example of interaction-driven quantum transport. The study, led by Jian-Song Pan of Sichuan University and colleagues Xiaofan Zhou, Wei Yi, and others from Shanxi University and University of Science and Technology of China, demonstrates this breakdown occurs in -flux rhombic lattices as interactions modify the phase accumulation of quantum paths. This alters the wave interference previously responsible for confinement. The team utilizes a newly defined concept, evolution-path symmetry (EPS), framing it as the invariance of a path’s contribution under combined geometric and phase transformations, establishing EPS as a tool for understanding complex transport phenomena beyond conventional eigenstate analysis.

Interaction-Driven Delocalization in -Flux Rhombic Lattices

Researchers exploring -flux rhombic lattices demonstrate that the destruction of Aharonov-Bohm (AB) caging is an example of interaction-driven quantum transport, where particles are localized due to interference when interactions are introduced. The team’s work focuses on a -flux rhombic lattice, a geometric arrangement where interactions disrupt EPS by modifying phase accumulation. This phase modification is the mechanism lifting the destructive interference responsible for AB caging, allowing particles to move freely. Detailed analysis of evolution paths in two-particle Fock space reveals the underlying physics. The researchers analyze paths connecting a doublon state, two particles occupying the same site, to a neighboring location within the lattice. Each path, visualized with single and correlated hopping amplitudes, contributes to the overall quantum evolution. Interactions introduce a crucial change: in the non-interacting limit, these paths interfere destructively, enforcing localization. However, when interactions are present, paths involving intermediate double occupancy acquire additional phase shifts. These shifts selectively modify the phase accumulation, breaking the EPS and enabling delocalization. Figures presented in the study visually confirm this process, showing a two-particle doublon initially confined to a single site rapidly spreading across the lattice when interactions are activated.

The established understanding of particle confinement within geometric structures is undergoing revision as new research demonstrates how interactions between particles dismantle these cages, triggering quantum transport. While Anderson localization and AB caging both rely on destructive interference, the introduction of interactions fundamentally alters this dynamic, moving beyond simply observing transport and instead pinpointing the breakdown of confinement mechanisms. Researchers are now focusing on a unifying principle to explain these interaction-driven changes, rather than fragmented explanations like bound-state formation or spectral weight redistribution.

In flux ladders, interactions break the phase relationship between symmetric paths, leading to a non-vanishing chiral current.

Chiral Transport Mechanisms in Flux Ladders

Extending this analysis to flux ladders, quasi-one-dimensional counterparts of the Harper-Hofstadter model, the team reveals a similar breakdown of symmetry. This chiral transport, previously attributed to interaction-induced spectral weight redistribution or vortex crystal formation, is now framed within the EPS framework. The researchers explain that interactions break the phase symmetry between pairs of paths related by chiral reflection, effectively enabling particle flow.

The conventional understanding of quantum transport in geometrically frustrated systems receives a significant refinement with the demonstration that the destruction of Aharonov-Bohm (AB) caging is an example of interaction-driven quantum transport. Specifically, the researchers demonstrate that intermediate double occupancy acquires additional interaction-induced phase shifts when interactions are present. The analysis reveals that interactions selectively alter the phase of paths involving double occupancy, effectively lifting the destructive interference that previously localized particles.