Crystal field excitations in a new Jeff =1/2 triangular lattice spin liquid

Quantum spin liquids (QSL) represent a highly entangled state of matter characterized by the absence of symmetry-breaking phase transition despite strong exchange interactions between its magnetic constituents, short- range spin correlations, and exotic fractional excitations. Rare-earth based frustrated triangular lattice antiferromagnets wherein a subtle interplay between competing degrees of freedom provides a novel route for realizing the enigmatic QSL state. The recently synthesized structurally perfect triangular lattice, K3NdTe2O9 is a promising candidate in this context. The localized Nd3+ spins on the triangular lattice show neither magnetic order nor spin-freezing state down to 60 mK, suggesting a dynamic state. Thermodynamic data reveal an effective Jeff = 1/2 (Nd3+) in the Kramers doublet ground state and a weak antiferromagnetic interaction Jex≈ 1 K between Jeff = 1/2 moments-typical for rare-earth based frustrated magnets owing to the localized nature of 4f orbitals. The magnetic specific heat shows an anomaly ~120 mK, however, the entropy release at this temperature doesn’t correspond to that expected for Jeff = ½. This calls for a very sensitive local probe such as Inelastic Neutron Scattering to track low-energy excitations. The low-energy excitations possibly include that emerge from the crystal electric field, which are essential to understand the magnetism and anisotropy of the compound under study.