Gapless spin liquid behavior in a kagome Heisenberg antiferromagnet with randomly distributed hexagons of alternate bonds

Jiabin Liu, Long Yuan, Xuan Li, Boqiang Li, Kan Zhao, Haijun Liao, and Yuesheng Li
Phys. Rev. B 105, 024418 – Published 18 January 2022

Abstract

We demonstrate that the single crystal of YCu3[OH(D)]6.5Br2.5 (YCOB) is a kagome Heisenberg antiferromagnet without evident orphan spins (0.8%). The site mixing between polar OH and nonpolar Br causes local distortions of Cu–O–Cu exchange paths and gives rise to 70(2)% of randomly distributed hexagons of alternate bonds (J1ΔJ and J1+ΔJ) and the rest of the almost-uniform hexagons (J1) on the kagome lattice. Simulations of the random exchange model with ΔJ/J1 = 0.7(1) show good agreement with experimental observations, including the weak upturn seen in susceptibility and the slight polarization in magnetization. Despite the average antiferromagnetic coupling of J160 K, no conventional freezing is observed down to T0.001J1, and the raw specific heat exhibits a nearly quadratic temperature dependence below 1 K 0.02J1, phenomenologically consistent with a gapless (spin gap 0.025J1) Dirac quantum spin liquid (QSL). Our result sheds light on the theoretical understanding of the randomness-relevant gapless QSL behavior in YCOB, as well as in other relevant materials.

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  • Received 26 July 2021
  • Revised 4 January 2022
  • Accepted 10 January 2022

DOI:https://doi.org/10.1103/PhysRevB.105.024418

©2022 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Jiabin Liu1,*, Long Yuan1,*, Xuan Li2,3,*, Boqiang Li1, Kan Zhao4, Haijun Liao2,5,†, and Yuesheng Li1,‡

  • 1Wuhan National High Magnetic Field Center and School of Physics, Huazhong University of Science and Technology, 430074 Wuhan, China
  • 2Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190, China
  • 3University of Chinese Academy of Sciences, Beijing 100049, China
  • 4School of Physics, Beihang University, Beijing 100191, China
  • 5Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China

  • *These authors contributed equally to this paper.
  • navyphysics@iphy.ac.cn
  • yuesheng_li@hust.edu.cn

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Vol. 105, Iss. 2 — 1 January 2022

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