Discovery of ‘quantum’ supercritical state of electrons induced by valence fluctuation
The University of Tokyo
The group by research fellow Kentaro Kuga (affiliated at the time of the research), research associate Yosuke Matsumoto (affiliated at the time of the research), professor Satoru Nakatsuji and others at the Institute for Solid State Physics, the University of Tokyo (Director Masashi Takigawa), in collaboration with RIKEN (President Hiroshi Matsumoto) SPring-8 Center, has discovered a crossover where the valence of the ytterbium ion changes rapidly by adding a very small amount (~ 1.4%) of iron into the ytterbium compound (α-YbAl1-xFexB4). The valence was measured by hard X-ray photoemission spectroscopy using SPring-8 RIKEN beamline BL29XU. The valence is unstable around the crossover region and the large critical valence fluctuation is expected.
In addition to the valence crossover, the group discovered a strange metallic state that did not show magnetic order down to absolute zero temperature (non-magnetic properties) in spite that magnetization became quite large (magnetic properties). The discovery of both a valence crossover and a strange metallic state indicates the fluctuation between the high valence state exhibiting magnetic properties and the low valence state showing nonmagnetic properties (figure). The detailed analysis of the magnetization also indicated that the quantum critical point exists at the 1.4% of the additive amount of iron and at the absolute zero temperature. This is the first discovery in the world to illustrate the quantum valence critical point and the existence of its related strange metallic state. It is also true that the supercritical fluid that is being widely applied industrially has realized in the form of valence change. It is expected to facilitate discovery of “quantum” supercritical fluids in fluids like water and carbon dioxide.
This research paper was published on the online edition of Science Advances, the U.S. science journal on February 23, 2018.
- Journal: Science Advances (2018)
- Title: Quantum Valence Criticality in a Correlated Metal
- Author: Kentaro Kuga+, Yosuke Matsumoto+, Mario Okawa, Shintaro Suzuki, Takahiro Tomita, Keita Sone, Yasuyuki Shimura, Toshiro Sakakibara, Daisuke Nishio-Hamane, Yoshitomo Karaki, Yasutaka Takata, Masaharu Matsunami, Ritsuko Eguchi, Munetaka Taguchi, Ashish Chainani, Shik Shin, Kenji Tamasaku, Yoshinori Nishino, Makina Yabashi, Tetsuya Ishikawa, Satoru Nakatsuji* (+:equal contribution, * Corresponding author)
- DOI: 10.1126/sciadv.aao3547