Research: Quantum Coulomb Liquids of Different Rank in the Breathing Pyrochlore Antiferromagnet

Magnetic pyrochlores have proven to be an excellent platform for the study of highly-correlated many-body phenomena, including spin liquids, and a variety of non-conventional ordered phases. In this work, we consider a spin model in the breathing pyrochlore lattice and study the various magnetic phases realized in the system. For the classical model, this system hosts two U(1) classical spin liquids, and one long-ranged ordered phase. These classical spin liquids are only stable for a constrained set of parameters where an extended ground-state degeneracy is achieved. For the quantum model, we find that the system not only hosts the magnetically ordered phase and the quantum analogues of the spin liquids realized in the classical model, but also realizes two additional non-conventional magnetic ordered phases, including an incommensurate spiral phase. We further demonstrate that the introduction of quantum fluctuations further stabilizes these spin liquids, yielding a broader range of interaction parameters where these disordered phases are realized. Our results establish the breathing pyrochlore as a promising and experimentally relevant platform where higher-rank gauge constraints, conventional magnetic order, and fluctuation-driven quantum phases compete on equal footing.

L. Gresista, D. Lozano-Gómez, M. Vojta, S. Trebst, Y. Iqbal,
Quantum Coulomb Liquids of Different Rank in the Breathing Pyrochlore Antiferromagnet,
​​​​​​​Phys. Rev. Lett. 137, 066504 (2026) (arXiv)