Theory of Ca${}_{10}$Cr${}_7$O${}_{28}$ as a bilayer breathing-kagome magnet: Classical thermodynamics and semi-classical dynamics

Abstract

Ca${}_{10}$Cr${}_7$O${}_{28}$ is a novel spin-$1/2$ magnet exhibiting spin liquid behaviour which sets it apart from any previously studied model or material. However, understanding Ca${}_{10}$Cr${}_7$O${}_{28}$ presents a significant challenge, because the low symmetry of the crystal structure leads to very complex interactions, with up to seven inequivalent coupling parameters in the unit cell. Here we explore the origin of the spin-liquid behaviour in Ca${}_{10}$Cr${}_7$O${}_{28}$, starting from the simplest microscopic model consistent with experiment - a Heisenberg model on a single bilayer of the breathing-kagome (BBK) lattice. We use a combination of classical Monte Carlo (MC) simulation and (semi-)classical Molecular Dynamics (MD) simulation to explore the thermodynamic and dynamic properties of this model, and compare these with experimental results for Ca${}_{10}$Cr${}_7$O${}_{28}$. We uncover qualitatively different behaviours on different timescales, and argue that the ground state of Ca${}_{10}$Cr${}_7$O${}_{28}$ is born out of a slowly-fluctuating "spiral spin liquid", while faster fluctuations echo the U(1) spin liquid found in the kagome antiferromagnet. We also identify key differences between longitudinal and transverse spin excitations in applied magnetic field, and argue that these are a distinguishing feature of the spin liquid in the BBK model.

32 pages, 22 figures; two animation videos as supplementary files, see https://www.youtube.com/watch?v=GGug4w4MiKQ and https://www.youtube.com/watch?v=jSRF7MZTiNM

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Cited by in corpus (22)

• Spiral spin-liquid on a honeycomb lattice
• Multifarious skyrmion phases on a trilayer triangular lattice
• Semi-classical simulation of spin-1 magnets
• Low energy structure of spiral spin liquids
• Skyrmion fluid and bimeron glass protected by a chiral spin liquid on a kagome lattice
• Curie-law crossover in spin liquids
• Spiral-spin-liquid behaviors and persistent reciprocal kagomé structure in frustrated van der Waals magnets and beyond
• Stability of Skyrmion Crystal Phase in Centrosymmetric Distorted Triangular-Lattice Antiferromagnets
• Line-Graph Approach to Spiral Spin Liquids
• Spiral spin liquid in a frustrated honeycomb antiferromagnet: A single-crystal study of GdZnPO
• Spiral Spin Liquid Noise
• Observation of the spiral spin liquid in a triangular-lattice material
• Magnetic properties of the spiral spin liquid and surrounding phases in the square lattice XY model
• Thermodynamics of the dipole-octupole pyrochlore magnet Ce${}_2$Hf${}_2$O${}_7$ in applied magnetic fields
• Giant Magnetocaloric Effect in a Honeycomb Spiral Spin-Liquid Candidate
• Classical spin models of the windmill lattice and their relevance for PbCuTe${}_2$O${}_6$
• Dynamic Spin-Lattice Coupling and Statistical Interpretation for the Molecular-Like Excitations in Frustrated Pyrochlores
• Finite temperature tensor network algorithm for frustrated two-dimensional quantum materials
• Pinch points and half moons encode Berry curvature
• Strong coupling of lattice and orbital excitations in quantum magnet Ca${}_{10}$Cr${}_7$O${}_{28}$: Anomalous temperature dependence of Raman phonons
• Codimension-Two Spiral Spin-Liquid in the Effective Honeycomb-Lattice Compound Cs${}_3$Fe${}_2$Cl${}_9$
• Origin of the intermediate-temperature magnetic specific heat capacity in the spin-liquid candidate Ca${}_{10}$Cr${}_7$O${}_{28}$