Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany.
Department of Physics, Renmin University of China, Beijing 100872, China.
Nat Commun. 2017 Jun 22;8:15814. doi: 10.1038/ncomms15814.
Since its proposal by Anderson, resonating valence bonds (RVB) formed by a superposition of fluctuating singlet pairs have been a paradigmatic concept in understanding quantum spin liquids. Here, we show that excitations related to singlet breaking on nearest-neighbour bonds describe the high-energy part of the excitation spectrum in YbMgGaO, the effective spin-1/2 frustrated antiferromagnet on the triangular lattice, as originally considered by Anderson. By a thorough single-crystal inelastic neutron scattering study, we demonstrate that nearest-neighbour RVB excitations account for the bulk of the spectral weight above 0.5 meV. This renders YbMgGaO the first experimental system where putative RVB correlations restricted to nearest neighbours are observed, and poses a fundamental question of how complex interactions on the triangular lattice conspire to form this unique many-body state.
自安德森提出以来，由波动单态对叠加形成的共振价键（RVB）一直是理解量子自旋液体的典范概念。在这里，我们表明，与最近邻键上的单态破裂相关的激发描述了三角晶格上有效自旋为 1/2 的 frustrated antiferromagnet YbMgGaO 激发能谱的高能部分，这与安德森最初的考虑一致。通过彻底的单晶非弹性中子散射研究，我们证明了最近邻 RVB 激发解释了 0.5meV 以上光谱权重的大部分。这使得 YbMgGaO 成为第一个观察到仅限于最近邻的假定 RVB 相关性的实验体系，这提出了一个基本问题，即在三角晶格上的复杂相互作用如何协同形成这种独特的多体状态。
