论文标题
量子旋转候选$κ$ - （bedt-ttf）$ _ 2 $ -cu $ _2 $（CN）$ _ 3 $
Gapped magnetic ground state in quantum-spin-liquid candidate $κ$-(BEDT-TTF)$_2$-Cu$_2$(CN)$_3$
论文作者
论文摘要
几何挫败感，量子纠缠和混乱可能会防止具有强烈交换相互作用的局部旋转的远距离顺序，从而导致物质的新状态。 $κ$ - （bedt-ttf）$ _ 2 $ -cu $ _2 $（CN）$ _ 3 $被认为是此难以捉摸的量子型旋转状态的最佳近似值，但其基础属性仍然令人困惑。在这里，我们提出了一项多频电子旋转共振研究，直到Millikelvin温度，揭示了$ t^*= 6 \，\ Mathrm {k} $的旋转易感性迅速下降。旋转间隙的这种开口伴随着结构修改，这表明$ 6 \，\ mathrm {k} $ - 异常'，作为向价宽 - 固体基态的过渡。我们确定杂质的贡献，当固有的旋转形成单线时，该杂质贡献变得占主导地位。仅探测电子直接表现出缺陷的关键作用，对于没有磁性的量子旋转系统的低能特性。
Geometrical frustration, quantum entanglement and disorder may prevent long-range order of localized spins with strong exchange interactions, resulting in a novel state of matter. $κ$-(BEDT-TTF)$_2$-Cu$_2$(CN)$_3$ is considered the best approximation of this elusive quantum-spin-liquid state, but its ground-state properties remain puzzling. Here we present a multi-frequency electron-spin resonance study down to millikelvin temperatures, revealing a rapid drop of the spin susceptibility at $T^*=6\,\mathrm{K}$. This opening of a spin gap, accompanied by structural modifications, suggests the enigmatic `$6\,\mathrm{K}$-anomaly' as the transition to a valence-bond-solid ground state. We identify an impurity contribution that becomes dominant when the intrinsic spins form singlets. Only probing the electrons directly manifests the pivotal role of defects for the low-energy properties of quantum-spin systems without magnetic order.
