KCuCl $$_3$$ is known to show a quantum phase transition from the disordered to antiferromagnetically ordered phases by applying pressure. There is a longitudinal excitation mode (Higgs amplitude mode) in the vicinity of the quantum critical point in the ordered phase. To detect the Higgs amplitude mode, high-pressure ESR measurements are performed in KCuCl $$_3$$ . The experimental data are analyzed by the extended spin-wave theory on the basis of the vector spin chirality. We report the first ESR detection of the Higgs amplitude mode and the important role of the electric dipole described by the vector spin chirality.

中文翻译：

---

在二聚体系统 KCuCl$$_3$$ 中首次进行希格斯振幅模式的 ESR 检测和扩展自旋波理论分析

已知 KCuCl $$_3$$ 通过施加压力显示从无序到反铁磁有序相的量子相变。在有序相的量子临界点附近存在纵向激发模式（希格斯振幅模式）。为了检测希格斯振幅模式，在 KCuCl $$_3$$ 中执行高压 ESR 测量。在矢量自旋手征的基础上，利用扩展自旋波理论对实验数据进行了分析。我们报告了希格斯振幅模式的首次 ESR 检测以及矢量自旋手性描述的电偶极子的重要作用。