Pressure-induced color change arising from transformation between intra- and inter-band transitions in LuH$_{2\pm x}$N$_{y}$

• DOI: 10.48550/arxiv.2305.06103
• Publication Date: 2024-01-05
• Authors: Liu, Zhe; Zhang, Yingjie; Huang, Shenyang; Ming, Xue; Li, Qing; Pan, Chenghao; Dai, Yaomin; Zhou, Xiaoxiang; Zhu, Xiyu; Yan, Hugen; Wen, Hai-Hu
• Keywords: Superconductivity (cond-mat.supr-con); Condensed Matter - Materials Science; Condensed Matter - Superconductivity; Materials Science (cond-mat.mtrl-sci); FOS: Physical sciences

The pressure-induced color change in the nitrogen-doped lutetium hydride has triggered extensive discussions about the underlying physics. Here, we study the optical response of LuH$_{2 \pm x}$N$_{y}$ in a broad frequency range at ambient pressure and its evolution with pressure in the visible spectral range. The broad-band optical spectra at ambient pressure reveal a Drude component associated with intra-band electronic transitions and two Lorentz components (L1 and L2) arising from inter-band electronic transitions. The application of pressure causes a spectral weight transfer from L1 to the Drude component, leading to a blue shift of the plasma edge in the reflectivity spectrum alongside a reduction of the high-frequency reflectivity. Our results suggest that the pressure-induced color change in LuH$_{2 \pm x}$N$_{y}$ is closely related to the transformation between intra- and inter-band electronic transitions, providing new insights into the mechanism of the pressure-induced color change in LuH$_{2 \pm x}$N$_{y}$.<br/>20 pages, 4 figures. Comments are welcome and appreciated<br/>