Anomalous metallic behaviour in the doped spin liquid candidate κ-(ET)₄Hg_2.89Br₈

Quantum spin liquids are exotic Mott insulators that carry extraordinary spin excitations. Therefore, when doped, they are expected to afford metallic states with unconventional magnetic excitations. Here, we report experimental results which are suggestive of a doped spin liquid with anomalous metallicity in a triangular-lattice organic conductor. The spin susceptibility is nearly perfectly scaled to that of a non-doped spin liquid insulator in spite of the metallic state. Furthermore, the charge transport that is confined in the layer at high temperatures becomes sharply deconfined on cooling, coinciding with the rapid growth of spin correlations or coherence as signified by a steep decrease in spin susceptibility. The present results substantiate the desired doped spin liquid and suggest a strange metal, in which the coherence of the underlying spin liquid promotes the deconfinement of charge from the layers while preserving the non-Fermi-liquid nature.It is expected that introducing charge carriers into an exotic quantum spin liquid state may lead to an unconventional metal but there are no clear realizations of a metallic spin liquid. Here, the authors present a spin liquid candidate that also shows evidence of strange metal behavior.