SEPnet and Hubbard Theory Consortium, University of Kent, Canterbury CT2 7NH, United Kingdom.
ISIS facility, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot OX11 0QX, United Kingdom.
Phys Rev Lett. 2019 Aug 9;123(6):067204. doi: 10.1103/PhysRevLett.123.067204.
The spin ice materials Ho_{2}Ti_{2}O_{7} and Dy_{2}Ti_{2}O_{7} are by now perhaps the best-studied classical frustrated magnets. A crucial step towards the understanding of their low temperature behavior-both regarding their unusual dynamical properties and the possibility of observing their quantum coherent time evolution-is a quantitative understanding of the spin-flip processes which underpin the hopping of magnetic monopoles. We attack this problem in the framework of a quantum treatment of a single-ion subject to the crystal, exchange, and dipolar fields from neighboring ions. By studying the fundamental quantum mechanical mechanisms, we discover a bimodal distribution of hopping rates that depends on the local spin configuration, in broad agreement with rates extracted from experiment. Applying the same analysis to Pr_{2}Sn_{2}O_{7} and Pr_{2}Zr_{2}O_{7}, we find an even more pronounced separation of timescales signaling the likelihood of coherent many-body dynamics.
Ho_{2}Ti_{2}O_{7}和 Dy_{2}Ti_{2}O_{7}自旋冰材料或许是目前研究最为透彻的经典 frustrated magnets。为了理解它们的低温性质——包括其异常动力学特性以及观察量子相干时间演化的可能性——理解自旋翻转过程是至关重要的，这些过程是磁单极子跳跃的基础。我们在一个单离子的量子处理框架中解决这个问题，该框架考虑了来自相邻离子的晶体、交换和偶极场。通过研究基本的量子力学机制，我们发现跳跃速率存在双峰分布，这与实验中提取的速率有广泛的一致性。我们将相同的分析应用于 Pr_{2}Sn_{2}O_{7}和 Pr_{2}Zr_{2}O_{7}，发现了更明显的时间尺度分离，这表明相干多体动力学的可能性更大。
