Beecroft Building, Department of Physics, University of Oxford, Parks Road, Oxford, OX1 3PU
Professor Avinash V. Mahajan
Dr Koushik Karmakar
Abstract
We report the synthesis and properties of (H,Li)6Ru2O6, which is shown to be a Jeff = 1/2 system made out of Ru3+ moments in a honeycomb geometry. Bulk magnetization, heat capacity, nuclear magnetic resonance (NMR), and muon spin relaxation (SR) rule out the presence of static moments or any spin glass phase down to 500 mK. All techniques suggest a crossover to a liquid-like state below about 40 K. The 7Li NMR shift data suggest a non-zero T-independent spin susceptibility at low-T. In zero field, Cm/T shows T-0.9 divergence which is consistent with vacancy-induced effects on low-energy excitations of the pristine Kitaev spin liquid. With field, power-law variations in the 7Li NMR spin-lattice relaxation rate 1/T1 and magnetic heat capacity Cm show quantitatively new scaling behaviors. A two-step entropy release in heat capacity is also observed, putatively from Z2 flux (low-T step) and itinerant Majorana fermions (high-T step). Based on these findings, we propose that (H,Li)6Ru2O6 realizes a Kitaev spin liquid with no evidence of inherent magnetic ordering in zero field unlike -RuCl3 where an 8 Tesla field is required to suppress magnetic order.