Quantum spin liquids form an exotic class of quantum phases of matter, accompanied by emergent gauge fields, topological order and fractionalized excitations, with strong interaction effects and long-range entanglement.  The recently discovered material Ca₁₀Cr₇O₂₈ shows strong indications of hosting such a novel phase of matter, but with properties that sets it apart from any previously studied quantum spin liquid.
In this work, we make a crucial step towards understanding the nature and origin of the spin liquid behaviour in Ca₁₀Cr₇O₂₈. Using a combination of Monte Carlo and molecular dynamics simulation, and spin-wave calculations, we carry out a comprehensive study of a bilayer breathing kagome model derived from experiment. We identify the low-energy physics as being that of a spiral spin liquid, characterised by a “ring”-like feature in the spin structure factor. Meanwhile, at higher energies, we can trace the dynamical properties to a dynamical Columb spin liquid, found when the material is saturated in magnetic field. Hence we establish that Ca₁₀Cr₇O₂₈ is a rare case of a many-body system where two types of spin liquid coexist at different time scales.

This work was published as “Theory of Ca₁₀Cr₇O₂₈ as a bilayer breathing-kagome magnet: Classical thermodynamics and semi-classical dynamics” Rico Pohle, Han Yan and Nic Shannon, Phys. Rev. B 104, 024426 (2021)