Quantum spin liquid with the Ising character in the triangular-lattice antiferromagnet neodymium heptatantalate*

Quantum spin liquid (QSL) has in recent years become a key concept in the realm of quantum materials. This fascinating state of mater that is highly entangled, yet it preserves lattice symmetries, has been experimentally observed in a variety of geometrically frustrated materials, including a few realizations of the two-dimensional triangular spin lattice. However, in the majority of these materials the QSL state is intimately related to structural disorder.

We have recently discovered a QSL state in a novel triangular antiferromagnet neodymium heptatantalate, NdTa7O₁₉, in which no structural imperfections have been observed [1]. Our in-depth experimental study detected no magnetic ordering even at temperatures of only a few tens of millikelvins, much below the exchange-interaction scale of this compound. Furthermore, sizable Ising-like spin correlations between the nearest neighbors on the triangular lattice and persistent spin dynamics have been detected in the ground state. The QSL state in this rare-earth based material has been attributed to strong magnetic anisotropy. The investigated compound is a member of a broad rare-earth heptatantalate family, which is thus introduced as a novel generic framework for QSLs.

[1] T. Arh, B. Sana, M. Pregelj, P. Khuntia, Z. Jaglicic, M. D. Le, P. K. Biswas, P. Manuel, L. Mangin-Thro, A. Ozarowski, A. Zorko, The Ising triangular-lattice antiferromagnet neodymium heptatantalate as a quantum spin liquid candidate, Nat. Mater. 21, 416 (2022).