Mermin-Wagner physics, (H,T) phase diagram, and candidate quantum spin-liquid phase in the spin- 12 triangular-lattice antiferromagnet Ba8CoNb6O24 Academic Article uri icon

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  • Ba$_8$CoNb$_6$O$_{24}$ presents a system whose Co$^{2+}$ ions have an effective spin 1/2 and construct a regular triangular-lattice antiferromagnet (TLAFM) with a very large interlayer spacing, ensuring purely two-dimensional character. We exploit this ideal realization to perform a detailed experimental analysis of the $S = 1/2$ TLAFM, which is one of the keystone models in frustrated quantum magnetism. We find strong low-energy spin fluctuations and no magnetic ordering, but a diverging correlation length down to 0.1 K, indicating a Mermin-Wagner trend towards zero-temperature order. Below 0.1 K, however, our low-field measurements show an nexpected magnetically disordered state, which is a candidate quantum spin liquid. We establish the $(H,T)$ phase diagram, mapping in detail the quantum fluctuation corrections to the available theoretical analysis. These include a strong upshift in field of the maximum ordering temperature, qualitative changes to both low- and high-field phase boundaries, and an ordered regime apparently dominated by the collinear "up-up-down" state. Ba$_8$CoNb$_6$O$_{24}$ therefore offers fresh input for the development of theoretical approaches to the field-induced quantum phase transitions of the $S = 1/2$ Heisenberg TLAFM.


  • Cui, Y
  • Dai, J
  • Zhou, P
  • Wang, PS
  • Li, TR
  • Song, WH
  • Wang, JC
  • Ma, L
  • Zhang, Z
  • Li, SY
  • Luke, Graeme
  • Normand, B
  • Xiang, T
  • Yu, W

publication date

  • April 13, 2018