Observation of a $Pbca$ phase and robust metallicity in $\rm{RuO_2}$ under pressure

• DOI: 10.48550/arxiv.2502.06228
• Publication Date: 2025-02-10
• Authors: He Zhang; Xudong Wei; Zhong Wei; Xiaoli Ma; L. J. Wu; Jie Zhou; Saori I. Kawaguchi; Hirokazu Kadobayashi; Zhenxiang Cheng; Guoying Gao; Xiaohui Yu; Ho‐kwang Mao; Binbin Yue; Fang Hong
• Keywords: Condensed Matter - Materials Science; Materials Science (cond-mat.mtrl-sci); FOS: Physical sciences

$\rm{RuO_2}$ stands as a quintessential rutile-type compound under ambient conditions, with its structural exploration pressure bearing significant implications for both phase transition investigations and Earth science. Nonetheless, the precise sequence remains debate. In this study, we disclose emergence of $Pbca$ alongside enduring metallic character megabar pressure. Employing state-of-the-art synchrotron X-ray diffraction, our observations delineate trajectory progressing through rutile, $\rm{CaCl_2}$, ultimately phases. Notably, manifests immediately just after rutile-$\rm{CaCl_2}$ transition, confining narrow regime pure $\rm{CaCl_2}$-type phase. Within range 15.5 to 35.0 GPa, coexistence phases is observed, transforming sole presence beyond GPa. Electrical transport measurements conducted on single crystal powder samples confirm conductivity $\rm{RuO_2}$, persisting up at least $\sim$120 albeit exhibiting diminished ultrahigh pressures due reduction in electronic density states Fermi level. This study furnishes compelling evidence across broad range, diverging from previously widely acknowledged $Pa\bar{3}$ phase, thereby offering crucial insights into phenomena other metal dioxides advancing comprehension behaviors within 4d 5d electron systems.