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

TL;DR

This paper reports the experimental discovery of a quantum spin liquid state in a structurally perfect triangular-lattice antiferromagnet NdTa$_7$O$_{19}$, highlighting the role of strong spin-orbit coupling and magnetic anisotropy.

Contribution

It provides the first experimental confirmation of a quantum spin liquid in a rare-earth heptatantalate, emphasizing the importance of spin-orbit coupling in stabilizing such states.

Findings

Observation of low-frequency spin excitations down to the lowest temperatures.

Identification of Ising-like interactions with spin-1/2 degrees of freedom.

Highlighting the potential of rare-earth heptatantalates for quantum applications.

Abstract

Disordered magnetic states known as spin liquids are of paramount importance in both fundamental and applied science. A classical state of this kind was predicted for the Ising antiferromagnetic triangular model more than half a century ago, while additional non-commuting exchange terms were proposed to induce its quantum version -- a quantum spin liquid. These predictions have not been yet confirmed experimentally. Here we report a discovery of such a state in the structurally perfect triangular-lattice antiferromagnet NdTa$_7$O$_{19}$. Its magnetic ground state is characterized by spin-1/2 degrees of freedom with Ising-like interactions and gives rise to low-frequency spin excitations persisting down to the lowest temperatures. Our study demonstrates the key role of strong spin-orbit coupling in stabilizing spin liquids that result from magnetic anisotropy and highlights the large family of rare-earth (RE) heptatantalates RETa$_7$O$_{19}$ as a novel framework for realization of these states, which represent a promising platform for quantum applications.