(H, Li)6Ru2O6 (Ru3+, Jeff =1/2): a novel Kitaev Quantum Spin Liquid alternative to 𝛼-RuCl3

Kitaev Quantum Spin Liquids (KQSL) host novel ground state and excited state properties. A prominent example is α-RuCl3 having Ru3+ (Jeff = 1/2) on a honeycomb lattice. In zero applied field this compound is magnetically ordered and a field of 80 kOe is required to suppress the order and reveal the KQSL state. Herein we report the synthesis of (H, Li)6Ru2O6, with Ru3+ (Jeff = ½) on a honeycomb lattice. Our heat capacity measurements suggest no ordering down to 400 mK in spite of a large Curie-Weiss temperature of - 44 K as extracted from our susceptibility data. Our 7Li NMR measurements find a power law variation of the 7Li spin-lattice relaxation rate below 40 K. From zero-field muon spin relaxation, we find neither oscillations in the muon asymmetry nor any 1/3 tail in the muon asymmetry suggestive of the absence of long-range order and of the presence of dynamic moments. These results are similar to those of H3LiIr2O6 (suggested to be a KQSL) except that the saturation of the muon depolarisation rate λ in (H, Li)6Ru2O6 sets in at 10 times the temperature in H3LiIr2O6. Based on our data, we propose that (H, Li)6Ru2O6 is a KQSL even in zero field.