Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
Nat Commun. 2013;4:1934. doi: 10.1038/ncomms2914.
Spin ice is a magnetic analog of H2O ice that harbors dense static disorder. Dipolar interactions between classical spins yield a frozen frustrated state with residual configurational Pauling entropy and emergent magnetic monopolar quasiparticles. Introducing quantum fluctuations is of great interest as this could melt spin ice and allow coherent propagation of monopoles. Here, we report experimental evidence for quantum dynamics of magnetic monopolar quasiparticles in a new class of spin ice based on exchange interactions, Pr2Zr2O7. Narrow pinch point features in otherwise diffuse elastic neutron scattering reflects adherence to a divergence-free constraint for disordered spins on long time scales. Magnetic susceptibility and specific heat data correspondingly show exponentially activated behaviors. In sharp contrast to conventional ice, however, >90% of the neutron scattering is inelastic and devoid of pinch points furnishing evidence for magnetic monopolar quantum fluctuations.
自旋冰是 H2O 冰的磁学类比物，具有密集的静态无序性。经典自旋之间的偶极相互作用产生了一个冷冻的受挫状态，具有剩余的构型鲍林熵和新兴的磁单极准粒子。引入量子涨落是非常有趣的，因为这可能会使自旋冰融化，并允许单极子的相干传播。在这里，我们报告了基于交换相互作用的新型自旋冰中磁单极准粒子量子动力学的实验证据，Pr2Zr2O7。在其他扩散弹性中子散射中，狭窄的尖点特征反映了在长时间尺度上无序自旋的无散度约束。磁导率和比热数据相应地表现出指数激活行为。然而，与传统冰形成鲜明对比的是，>90%的中子散射是非弹性的，没有尖点，这为磁单极量子涨落提供了证据。
