We have investigated the elastic response of a transverse Ising magnet ${\mathrm{CoNb}}_2{\mathrm{O}}_6$ by means of ultrasound velocity measurement. A huge elastic anomaly in the $C_{66}$ mode is observed near a quantum critical point when sweeping a magnetic field perpendicular to the Ising axis. This anomaly appears to become critical only for the Faraday configuration (field parallel to the sound propagation direction) but is much less pronounced for the Voigt geometry (field perpendicular to the sound propagation direction). We propose that the relativistic spin-orbit interaction plays a crucial role in the quantum critical regime resulting in the elastic anomaly, which is enhanced by quantum fluctuations.

中文翻译：

---

横向Ising磁体中量子临界点附近的异常晶格软化

我们研究了横向Ising磁体的弹性响应 ${\mathrm{钴铌}}_2{\mathrm{Ø}}_6$通过超声波速度测量。巨大的弹性异常$C_{66}$当扫描垂直于Ising轴的磁场时，在量子临界点附近观察到模态。该异常似乎仅对于法拉第配置（平行于声音传播方向的场）变得很关键，而对于Voigt几何形状（垂直于声音传播方向的场）则不那么明显。我们提出，相对论自旋轨道相互作用在导致弹性异常的量子临界状态中起着至关重要的作用，这种异常被量子涨落所增强。