2017/09/30 by M. Gomilšek, M. Klanjšek, R. Žitko +6 · 2 citations
Physics and Astronomy · #cond-mat.str-el
paper · pdf · doi:10.1103/physrevlett.119.137205
published as Phys. Rev. Lett. 119, 137205 (2017) · minor corrections
arxiv created 2017/10/02 · arxiv updated 2017/10/03
The ground state of the quantum kagome antiferromagnet Zn-brochantite, ZnCu3(OH)6SO4, which is one of only a few known spin-liquid (SL) realizations in two or three dimensions, has been described as a gapless SL with a spinon Fermi surface. Employing nuclear magnetic resonance in a broad magnetic-field range down to millikelvin temperatures, we show that in applied magnetic fields this enigmatic state is intrinsically unstable against a SL with a full or a partial gap. A similar instability of the gapless Fermi-surface SL was previously encountered in an organic triangular-lattice antiferromagnet, suggesting a common destabilization mechanism that most likely arises from spinon pairing. A salient property of this instability is that an infinitesimal field suffices to induce it, as predicted theoretically for some other types of gapless SL's.