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arXiv · 2010.07900

Dynamic fingerprint of fractionalized excitations in single-crystalline Cu$_3$Zn(OH)$_6$FBr

Ying Fu·Miao-Ling Lin·Le Wang·Qiye Liu·Lianglong Huang·Wenrui Jiang·Zhanyang Hao·Cai Liu·Hu Zhang·Xingqiang Shi·Jun Zhang·Junfeng Dai·Dapeng Yu·Fei Ye·Patrick A. Lee·Ping-Heng Tan·Jia-Wei Mei
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Abstract

Quantum spin liquid (QSL) represents a new class of condensed matter states characterized by the long-range many-body entanglement of topological orders. The most prominent feature of the elusive QSL state is the existence of fractionalized spin excitations. Subject to the strong quantum fluctuations, the spin-1/2 antiferromagnetic system on a kagome lattice is the promising candidate for hosting a QSL ground state, but the structurally ideal realization is rare. Here, we report Raman scattering on the single crystalline Cu$_3$Zn(OH)$_6$FBr, and confirm that the ideal kagome structure remains down to low temperatures without any lattice distortion by the angle-resolved polarized Raman responses and second-harmonic-generation measurements. Furthermore, at low temperatures the Raman scattering reveals a continuum of the spin excitations in Cu$_3$Zn(OH)$_6$FBr, in contrast to the sharp magnon peak in the ordered kagome antiferromagnet EuCu$_3$(OH)$_6$Cl$_3$. Such magnetic Raman continuum, in particular, the substantial low-energy one-pair spinon excitation serves as strong evidence for fractionalized spin excitations in Cu$_3$Zn(OH)$_6$FBr.

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Ying Fu, Miao-Ling Lin, Le Wang, Qiye Liu, Lianglong Huang, Wenrui Jiang, Zhanyang Hao, Cai Liu, Hu Zhang, Xingqiang Shi, Jun Zhang, Junfeng Dai, Dapeng Yu, Fei Ye, Patrick A. Lee, Ping-Heng Tan, Jia-Wei Mei. 2020-10-15. Dynamic fingerprint of fractionalized excitations in single-crystalline Cu$_3$Zn(OH)$_6$FBr. https://doi.org/10.1038/s41467-021-23381-9

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