Freezing of the Lattice in the Kagome Lattice Heisenberg Antiferromagnet Zn-barlowite ZnCu${}_3$(OD)${}_6$FBr

Abstract

We use ${}^{79}$Br nuclear quadrupole resonance (NQR) to demonstrate that ultra slow lattice dynamics set in below the temperature scale set by the Cu-Cu super-exchange interaction $J$~($\simeq 160$~K) in the kagome lattice Heisenberg antiferromagnet Zn-barlowite. The lattice completely freezes below 50~K, and ${}^{79}$Br NQR lineshapes become twice broader due to increased lattice distortions. Moreover, the frozen lattice exhibits an oscillatory component in the transverse spin echo decay, a typical signature of pairing of nuclear spins by indirect nuclear spin-spin interaction. This indicates that some Br sites form structural dimers via a pair of kagome Cu sites prior to the gradual emergence of spin singlets below $\sim 30$~K. Our findings underscore the significant roles played by subtle structural distortions in determining the nature of the disordered magnetic ground state of the kagome lattice.

Phys. Rev. Lett. (in press)

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Cited by in corpus (7)

• Experimental signatures of quantum and topological states in frustrated magnetism
• Controlling frustrated magnetism on the kagome lattice by uniaxial-strain tuning
• Emergence of the spin polarized domains in the kagome lattice Heisenberg antiferromagnet Zn-barlowite (Zn${}_{0.95}$Cu${}_{0.05}$)Cu${}_3$(OD)${}_6$FBr
• High energy spin excitations in the quantum spin liquid candidate Zn-barlowite probed by resonant inelastic x-ray scattering
• NMR evidence of spinon localization in kagome antiferromagnet YCu${}_3$(OH)${}_6$Br${}_2$[Br${}_{1-x}$(OH)${}_x$]
• Pressure-tuned spin chains in brochantite, Cu${}_4$SO${}_4$(OH)${}_6$
• Local probe investigation of the spin dynamics in the kagome and inter-layers of orthorhombic barlowite Cu${}_4$(OD)${}_6$FBr: ${}^{79}$Br and ${}^{63}$Cu NQR study