(H,Li)₆Ru₂O₆ (Ru3+, J_eff=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 having Ru³⁺ (J_eff=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⁺ (J_eff=1/2) on a honeycomb lattice. Our heat capacity measurements suggest no ordering down to 400 mK in spite of a large Curie-Weiss temperature (- 44 K) as extracted from our susceptibility data. All techniques suggest a crossover to a liquid-like state below about 40 K. A two-step entropy release in heat capacity indicative of Z₂ flux (low-T) and itinerant Majorana fermions (high-T) is observed. The ⁷Li NMR shift shows non-zero T-independent spin susceptibility at low T. NMR 1/T₁ power law variation and data collapse/scaling with T/B are signatures of gapless excitations and (perhaps) a field-dependent Density of States DOS (E, B). The flattening/saturation of muon spin relaxation rate, λ (persistent spin dynamics) sets in at 10 times the temperature in H₃LiIr₂O₆ which is a KQSL. μSR asymmetry at low-T with time shows data-collapse when plotted vs t/B². The scaling behavior seen in C_m, 1/T_1, and also μSR asymmetry is indicative of underlying topological symmetry that emerges in the ground state. Based on these findings, we propose a possible KQSL in (H,Li)₆Ru₂O₆ with Ru³⁺ and no evidence of magnetic ordering, unlike α-RuCl₃.