Observation of the spiral spin liquid in a triangular-lattice material.

Andriushin, N D; Nikitin, S E; Fjellvåg, Ø S; White, J S; Podlesnyak, A; Inosov, D S; Rahn, M C; Schmidt, M et al. · Nat Commun · 2025

basic_science · Level V

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Abstract

The spiral spin liquid (SSL) is a highly degenerate state characterized by a continuous contour or surface in reciprocal space spanned by a spiral propagation vector. Although the SSL state has been predicted in a number of various theoretical models, very few materials are so far experimentally identified to host such a state. Via combined single-crystal wide-angle and small-angle neutron scattering, we report observation of the SSL in the quasi-two-dimensional delafossite-like AgCrSe<sub>2</sub>. We show that it is a very close realization of the ideal Heisenberg J<sub>1</sub>-J<sub>2</sub>-J<sub>3</sub> frustrated model on the triangular lattice. By supplementing our experimental results with microscopic spin-dynamics simulations, we demonstrate how such exotic magnetic states are driven by thermal fluctuations and exchange frustration.