Spin excitations and thermodynamics of the t-J model on the honeycomb lattice Artem A. Vladimirov, Dieter Ihle and Nikolay M. Plakida Eur. Phys. J. B, 91 8 (2018) 195 Published online: 30 August 2018 DOI: 10.1140/epjb/e2018-80712-x