Department of Physics and Astronomy, London Centre for Nanotechnology, University College London, 17-19 Gordon Street, London WC1H OAH, UK.
Nat Commun. 2013;4:1535. doi: 10.1038/ncomms2551.
Spin ice illustrates many unusual magnetic properties, including zero point entropy, emergent monopoles and a quasi liquid-gas transition. To reveal the quantum spin dynamics that underpin these phenomena is an experimental challenge. Here we show how crucial information is contained in the frequency dependence of the magnetic susceptibility and in its high frequency or adiabatic limit. The typical response of Dy(2)Ti(2)O(7) spin ice indicates that monopole diffusion is Brownian but is underpinned by spin tunnelling and is influenced by collective monopole interactions. The adiabatic response reveals evidence of driven monopole plasma oscillations in weak applied field, and unconventional critical behaviour in strong applied field. Our results clarify the origin of the relatively high frequency response in spin ice. They disclose unexpected physics and establish adiabatic susceptibility as a revealing characteristic of exotic spin systems.
自旋冰展示了许多不寻常的磁性质，包括零点熵、涌现的单极子和准液-气相变。揭示支持这些现象的量子自旋动力学是一个实验挑战。在这里，我们展示了磁导率的频率依赖性及其高频或绝热极限中包含了哪些关键信息。Dy(2)Ti(2)O(7)自旋冰的典型响应表明，单极子扩散是布朗运动，但由自旋隧道效应支撑，并受到集体单极子相互作用的影响。绝热响应揭示了在弱外场中驱动单极子等离子体振荡的证据，以及在外场较强时的非常规临界行为。我们的结果澄清了自旋冰中相对高频响应的起源。它们揭示了意想不到的物理性质，并确立了绝热磁化率作为奇异自旋系统的一个有启发性的特征。
