Possible chiral classical spin liquid ground state in a tetra-trillium lattice antiferromagnet K2Fe2(MoO4)(PO4)2

Quantum materials, wherein frustration, electronic band topology, spin correlations, and their
interplay exist, can harbor a panoply of novel quantum states, including quantum spin liquids (QSLs), spin
ices, and fractional quantum Hall liquids. Theoretical calculations suggest various QSL types depending on spin-lattice symmetry, including
the chiral spin liquid (CSL), which lacks long-range order but breaks both time-reversal and parity
symmetries. The experimental realization of the CSL state in magnetic materials, however, remains a
significant challenge. Here,
we focus on a new chiral network of tetra-trillium lattice of Fe3+ ions. Neither magnetic
susceptibility nor specific-heat data show any signature of magnetic ordering down to 1.9 K
despite a large Curie-Weiss temperature of - 44 K. The magnetic specific heat indicates the
presence of short-range spin correlations and a gapless spin excitation spectrum. We
propose a muSR study much below the sub-Kelvin temperatures to unambiguously confirm
the ground state of classical CSL and identify the associated magnetic excitations in this new three-dimensional
frustrated magnet.