Institute for Quantum Matter, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA.
1] Institute for Quantum Matter, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA [2] NIST Center for Neutron Research, NIST, Gaithersburg, Maryland 20899, USA.
Nat Commun. 2014 Sep 18;5:4970. doi: 10.1038/ncomms5970.
In condensed matter systems, formation of long-range order (LRO) is often accompanied by new excitations. However, in many geometrically frustrated magnetic systems, conventional LRO is suppressed, while non-trivial spin correlations are still observed. A natural question to ask is then what is the nature of the excitations in this highly correlated state without broken symmetry? Frequently, applying a symmetry breaking field stabilizes excitations whose properties reflect certain aspects of the anomalous state without LRO. Here we report a THz spectroscopy study of novel excitations in quantum spin ice Yb2Ti2O7 under a <001> directed magnetic field. At large positive fields, both right- and left-handed magnon and two-magnon-like excitations are observed. The g-factors of these excitations are dramatically enhanced in the low-field limit, showing a crossover of these states into features consistent with the quantum string-like excitations proposed to exist in quantum spin ice in small <001> fields.
在凝聚态系统中，长程有序（LRO）的形成通常伴随着新的激发。然而，在许多几何上受挫的磁性系统中，传统的 LRO 被抑制，而仍然观察到非平凡的自旋关联。那么，在没有对称破缺的情况下，这个高度关联状态中的激发的性质是什么呢？通常，施加对称破缺场可以稳定激发，其性质反映了没有 LRO 的异常状态的某些方面。在这里，我们报告了在<001>方向磁场下量子自旋冰 Yb2Ti2O7 中新型激发的太赫兹光谱研究。在大的正场下，观察到右和左手磁子以及双磁子类似的激发。这些激发的 g 因子在低场极限下显著增强，表明这些状态的交叉进入与量子字符串样激发一致，这些激发被认为存在于小<001>场中的量子自旋冰中。
