Sarte P M, Aczel A A, Ehlers G, Stock C, Gaulin B D, Mauws C, Stone M B, Calder S, Nagler S E, Hollett J W, Zhou H D, Gardner J S, Attfield J P, Wiebe C R
School of Chemistry, University of Edinburgh, Edinburgh EH9 3FJ, United Kingdom. Centre for Science at Extreme Conditions, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom.
J Phys Condens Matter. 2017 Nov 15;29(45):45LT01. doi: 10.1088/1361-648X/aa8ec2. Epub 2017 Oct 19.
Magnetic monopoles are hypothesised elementary particles connected by Dirac strings that behave like infinitely thin solenoids (Dirac 1931 Proc. R. Soc. A 133 60). Despite decades of searching, free magnetic monopoles and their Dirac strings have eluded experimental detection, although there is substantial evidence for deconfined magnetic monopole quasiparticles in spin ice materials (Castelnovo et al 2008 Nature 326 411). Here we report the detection of a hierarchy of unequally-spaced magnetic excitations via high resolution inelastic neutron spectroscopic measurements on the quantum spin ice candidate [Formula: see text] [Formula: see text] [Formula: see text]. These excitations are well-described by a simple model of monopole pairs bound by a linear potential (Coldea et al Science 327 177) with an effective tension of 0.642(8) K [Formula: see text] at 1.65 K. The success of the linear potential model suggests that these low energy magnetic excitations are direct spectroscopic evidence for the confinement of magnetic monopole quasiparticles in the quantum spin ice candidate [Formula: see text] [Formula: see text] [Formula: see text].
磁单极子是一种假设的基本粒子，由狄拉克弦连接，其行为类似于无限细的螺线管（狄拉克，1931年，《皇家学会学报A》133卷，60页）。尽管经过数十年的搜寻，自由磁单极子及其狄拉克弦仍未被实验检测到，不过在自旋冰材料中存在大量关于退禁闭磁单极子准粒子的证据（卡斯泰尔诺沃等人，2008年，《自然》326卷，411页）。在此，我们报告通过对量子自旋冰候选物[化学式：见正文][化学式：见正文][化学式：见正文]进行高分辨率非弹性中子光谱测量，检测到了一系列不等间距的磁激发。这些激发可以通过一个由线性势束缚的单极子对的简单模型很好地描述（科尔迪亚等人，《科学》327卷，177页），在1.65K时有效张力为0.642(8)K[化学式：见正文]。线性势模型的成功表明，这些低能磁激发是量子自旋冰候选物[化学式：见正文][化学式：见正文][化学式：见正文]中磁单极子准粒子被禁闭的直接光谱证据。
