Magnetic Field Induced Quantum Spin Liquid in the Two Coupled Trillium Lattices of K 2 Ni 2 ( SO 4 ) 3

Quantum spin liquids are exotic states of matter that form when strongly frustrated magnetic interactions induce a highly entangled quantum paramagnet far below the energy scale of the magnetic interactions. Three-dimensional cases are especially challenging due to the significant reduction of the influence of quantum fluctuations. Here, we report the magnetic characterization of ${\mathrm{K}}_{2}{\mathrm{Ni}}_{2}({\mathrm{SO}}_{4}{)}_{3}$ forming a three-dimensional network of ${\mathrm{Ni}}^{2+}$ spins. Using density functional theory calculations, we show that this network consists of two interconnected spin-1 trillium lattices. In the absence of a magnetic field, magnetization, specific heat, neutron scattering, and muon spin relaxation experiments demonstrate a highly correlated and dynamic state, coexisting with a peculiar, very small static component exhibiting a strongly renormalized moment. A magnetic field $B\ensuremath{\gtrsim}4\text{ }\text{ }\mathrm{T}$ diminishes the ordered component and drives the system into a pure quantum spin liquid state. This shows that a system of interconnected $S=1$ trillium lattices exhibits a significantly elevated level of geometrical frustration.