Site-Specific Structure at Multiple Length Scales in Kagome Quantum Spin Liquid Candidates

Abstract

Realizing a quantum spin liquid (QSL) ground state in a real material is a leading issue in condensed matter physics research. In this pursuit, it is crucial to fully characterize the structure and influence of defects, as these can significantly affect the fragile QSL physics. Here, we perform a variety of cutting-edge synchrotron X-ray scattering and spectroscopy techniques, and we advance new methodologies for site-specific diffraction and L-edge Zn absorption spectroscopy. The experimental results along with our first-principles calculations address outstanding questions about the local and long-range structures of the two leading kagome QSL candidates, Zn-substituted barlowite Cu${}_3$Zn${}_x$Cu${}_{1-x}$(OH)${}_6$FBr and herbertsmithite Cu${}_3$Zn(OH)${}_6$Cl${}_2$. On all length scales probed, there is no evidence that Zn substitutes onto the kagome layers, thereby preserving the QSL physics of the kagome lattice. Our calculations show that antisite disorder is not energetically favorable and is even less favorable in Zn-barlowite compared to herbertsmithite. Site-specific X-ray diffraction measurements of Zn-barlowite reveal that Cu${}^{2+}$ and Zn${}^{2+}$ selectively occupy distinct interlayer sites, in contrast to herbertsmithite. Using the first measured Zn L-edge inelastic X-ray absorption spectra combined with calculations, we discover a systematic correlation between the loss of inversion symmetry from pseudo-octahedral (herbertsmithite) to trigonal prismatic coordination (Zn-barlowite) with the emergence of a new peak. Overall, our measurements suggest that Zn-barlowite has structural advantages over herbertsmithite that make its magnetic properties closer to an ideal QSL candidate: its kagome layers are highly resistant to nonmagnetic defects while the interlayers can accommodate a higher amount of Zn substitution.

13 pages, 6 figures

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Cited by in corpus (16)

• Emergence of spin singlets with inhomogeneous gaps in the kagome Heisenberg antiferromagnets Zn-barlowite and herbertsmithite
• Heat Transport in Herbertsmithite: Can a Quantum Spin Liquid Survive Disorder?
• Unconventional Magnetic Oscillations in Kagome Mott Insulators
• Controlling frustrated magnetism on the kagome lattice by uniaxial-strain tuning
• Specific Heat of the Kagome Antiferromagnet Herbertsmithite in High Magnetic Fields
• Freezing of the Lattice in the Kagome Lattice Heisenberg Antiferromagnet Zn-barlowite ZnCu${}_3$(OD)${}_6$FBr
• 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
• Heat conduction in herbertsmithite: field dependence at the onset of the quantum spin liquid regime
• Combinatorial exploration of quantum spin liquid candidates in the herbertsmithite material family
• Strong relevance of Zinc impurity in the spin-$\frac{1}{2}$ Kagome quantum antiferromagnets: a variational study
• Is Herbertsmithite far from an ideal antiferromagnet? Ab-initio answer including in-plane Dzyaloshinskii-Moriya interactions and coupling with extra-plane impurities
• Lattice dynamics of the frustrated kagome compound Y-kapellasite
• Spinon mediation of witness spin dynamics in herbertsmithite
• 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
• Spin Liquid Mimicry in the Hydroxide Double Perovskite CuSn(OH)${}_6$ Induced by Correlated Proton Disorder