Nonlocal effects of low-energy excitations in quantum-spin-liquid candidate Cu${}_3$Zn(OH)${}_6$FBr

Abstract

We systematically study the low-temperature specific heats for the two-dimensional kagome antiferromagnet, Cu${}_3$Zn(OH)${}_6$FBr. The specific heat exhibits a $T^{1.7}$ dependence at low temperatures and a shoulder-like feature above it. We construct a microscopic lattice model of $Z_2$ quantum spin liquid and perform large-scale quantum Monte Carlo simulations to show that the above behaviors come from the contributions from gapped anyons and magnetic impurities. Surprisingly, we find the entropy associated with the shoulder decreases quickly with grain size $d$, although the system is paramagnetic to the lowest temperature. While this can be simply explained by a core-shell picture in that the contribution from the interior state disappears near the surface, the 5.9-nm shell width precludes any trivial explanations. Such a large length scale signifies the coherence length of the nonlocality of the quantum entangled excitations in quantum spin liquid candidate, similar to Pippard's coherence length in superconductors. Our approach therefore offers a new experimental probe of the intangible quantum state of matter with topological order.

6 pages, 3 figures

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• Projected wavefunction study of Spin-1/2 Heisenberg model on the Kagome lattice
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• Choreographed entangle dances: topological states of quantum matter
• Gapless ground state in the archetypal quantum kagome antiferromagnet ZnCu${}_3$(OH)${}_6$Cl${}_2$
• Barlowite: A Spin-1/2 Antiferromagnet with a Geometrically Perfect Kagome Motif
• Spin liquid phase in a $S=1/2$ quantum magnet on the kagome lattice
• Magnetic phase diagram of Cu${}_{4-x}$Zn${}_x$(OH)${}_6$FBr studied by neutron-diffraction and $\mu$SR techniques

Cited by in corpus (6)

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• Magnetic ground states in kagome YCu${}_3$(OH)${}_6$[(Cl${}_x$Br${}_{1-x}$)${}_{3-y}$(OH)${}_y$]
• Pressure-induced superconductivity in flat-band Kagome compounds Pd${}_3$P${}_2$(S${}_{1-x}$Se${}_x$)${}_8$
• Spin excitations arising from anisotropic Dirac spinons in YCu${}_3$(OD)${}_6$Br${}_2$[Br${}_{0.33}$(OD)${}_{0.67}$]
• An integrated theoretical and numerical approach to understand modern experiments on quantum magnetism