The observation of quantum fluctuations in a kagome Heisenberg antiferromagnet

The search for the experimental evidence of quantum spin liquid (QSL) states is critical but extremely challenging, as the quenched interaction randomness introduced by structural imperfection is usually inevitable in real materials. YCu 3 (OH) 6.5 Br 2.5 (YCOB) is a spin-1/2 kagome Heisenberg antif...

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Bibliographic Details
Published in:Communications physics 2022-11, Vol.5 (1), p.1-8, Article 272
Main Authors: Lu, Fangjun, Yuan, Long, Zhang, Jian, Li, Boqiang, Luo, Yongkang, Li, Yuesheng
Format: Article
Language:English
Subjects:
639/766/119/995
639/766/119/997
Antiferromagnetism
Freezing
Hexagons
Low temperature
NMR
Nuclear magnetic resonance
Physics
Physics and Astronomy
Quenching
Randomness
Single crystals
Spin dynamics
Spin liquid
Spin-lattice relaxation
Temperature dependence
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Summary:The search for the experimental evidence of quantum spin liquid (QSL) states is critical but extremely challenging, as the quenched interaction randomness introduced by structural imperfection is usually inevitable in real materials. YCu 3 (OH) 6.5 Br 2.5 (YCOB) is a spin-1/2 kagome Heisenberg antiferromagnet (KHA) with strong coupling of 〈 J 1 〉 ~ 51 K but without conventional magnetic freezing down to 50 mK ~ 0.001〈 J 1 〉. Here, we report a Br nuclear magnetic resonance (NMR) study of the local spin susceptibility and dynamics on the single crystal of YCOB. The temperature dependence of NMR main-line shifts and broadening can be well understood within the frame of the KHA model with randomly distributed hexagons of alternate exchanges, compatible with the formation of a randomness-induced QSL state at low temperatures. The in-plane spin fluctuations as measured by the spin-lattice relaxation rates (1/ T 1 ) exhibit a weak temperature dependence down to T  ~ 0.03〈 J 1 〉. Our results demonstrate that the majority of spins remain highly fluctuating at low temperatures despite the quenched disorder in YCOB. In search of a quantum spin liquid, spin dynamics in a recently proposed candidate, kagome material YCu 3 (OH) 6.5 Br 2.5 was investigated by nuclear magnetic resonance. The work highlights the role of quantum fluctuations in the presence of random disorder in relation to gapless quantum spin liquids.
ISSN:2399-3650
2399-3650
DOI:10.1038/s42005-022-01053-4