Heat transport of the kagomé Heisenberg quantum spin liquid candidate YCu${}_3$(OH)${}_{6.5}$Br${}_{2.5}$: localized magnetic excitations and spin gap

Abstract

The spin-1/2 kagomé Heisenberg antiferromagnet is generally accepted as one of the most promising two-dimensional models to realize a quantum spin liquid state. Previous experimental efforts were almost exclusively on only one archetypal material, the herbertsmithite ZnCu${}_3$(OH)${}_6$Cl${}_2$, which unfortunately suffers from the notorious orphan spins problem caused by magnetic disorders. Here we turn to YCu${}_3$(OH)${}_{6.5}$Br${}_{2.5}$, recently recognized as another host of a globally undistorted kagomé Cu${}^{2+}$ lattice free from the orphan spins, thus a more feasible system for studying the intrinsic kagomé quantum spin liquid physics. Our high-resolution low-temperature thermal conductivity measurements yield a vanishing small residual linear term of $\kappa /T$ ($T\to 0$), and thus clearly rule out itinerant gapless fermionic excitations. Unusual scattering of phonons grows exponentially with temperature, suggesting thermally activated phonon-spin scattering and hence a gapped magnetic excitation, consistent with a ${\mathbb{Z}}_2$ quantum spin liquid ground state. Additionally, the analysis of magnetic field impact on the thermal conductivity reveals a field closing of the spin gap, while the excitations remain localized.

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References in corpus (9)

• Spin Dynamics of the Spin-1/2 Kagome Lattice Antiferromagnet ZnCu_3(OH)_6Cl_2
• Identifying Topological Order by Entanglement Entropy
• Projected wavefunction study of Spin-1/2 Heisenberg model on the Kagome lattice
• Emergence of nontrivial magnetic excitations in a spin liquid state of kagome volborthite
• Possible Dirac quantum spin liquid in a kagome quantum antiferromagnet YCu${}_3$(OH)${}_6$Br${}_2$[Br${}_x$(OH)${}_{1-x}$]
• Gapless Spin Liquid Behavior in A Kagome Heisenberg Antiferromagnet with Randomly Distributed Hexagons of Alternate Bonds
• Heat Transport in Herbertsmithite: Can a Quantum Spin Liquid Survive Disorder?
• Presence and absence of itinerant gapless excitations in the quantum spin liquid candidate EtMe${}_3$Sb[Pd(dmit)${}_2$]${}_2$
• Thermal transport of the frustrated spin-chain mineral linarite: Magnetic heat transport and strong spin-phonon scattering

Cited by in corpus (15)

• Spectral evidence for Dirac spinons in a kagome lattice antiferromagnet
• Emergent spin-gapped magnetization plateaus in a spin-1/2 perfect kagome antiferromagnet
• Kitaev Quantum Spin Liquids
• Unconventional Magnetic Oscillations in Kagome Mott Insulators
• Magnetic ground states in kagome YCu${}_3$(OH)${}_6$[(Cl${}_x$Br${}_{1-x}$)${}_{3-y}$(OH)${}_y$]
• NMR evidence of spinon localization in kagome antiferromagnet YCu${}_3$(OH)${}_6$Br${}_2$[Br${}_{1-x}$(OH)${}_x$]
• Thermodynamic evidence of fermionic behavior in the vicinity of one-ninth plateau in a kagome antiferromagnet
• Quantum annealing of a frustrated magnet
• Chemo-Structural Disorder in the kagomé spin $S$ = 1/2 systems ZnCu${}_3$(OH)${}_6$Cl${}_2$ and YCu${}_3$(OH)${}_6$Br${}_2$[Br${}_x$(OH)${}_{1-x}$]
• Spin excitations arising from anisotropic Dirac spinons in YCu${}_3$(OD)${}_6$Br${}_2$[Br${}_{0.33}$(OD)${}_{0.67}$]
• Recent progress in quantum spin liquids, fractional magnetization plateaus, and unconventional superconductivity in kagome lattices
• Continuous order-to-order quantum phase transitions from fixed-point annihilation
• Disorder-induced spin-cluster magnetism in a doped kagome spin liquid candidate
• Itinerant and topological excitations in a honeycomb spiral spin liquid candidate
• Exerting chemical pressure on the kagome lattice as frustration control in the kapellasite family $A$Cu${}_3$(OH)${}_{6+x}$(Cl,Br)${}_{3-x}$