Quantum Paramagnet Near Spin-State Transition

Keisuke Tomiyasu, Naoko Ito, Ryuji Okazaki, Yuki Takahashi, Mitsugi Onodera, Kazuaki Iwasa, Tsutomu Nojima, Takuya Aoyama, Kenya Ohgushi, Yoshihisa Ishikawa, Takashi Kamiyama, Seiko Ohira-Kawamura, Maiko Kofu, Sumio Ishihara

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


Spin-state transition, also known as spin crossover, plays a key role in diverse systems, including minerals and biological materials. In theory, the boundary range between the low- and high-spin states is expected to enrich the transition and give rise to unusual physical states. However, no compound that realizes a nearly degenerate critical range as the ground state without requiring special external conditions has yet been experimentally identified. This study reports that, by comprehensive measurements of macroscopic physical properties, X-ray diffractometry, and neutron spectroscopy, the Sc substitution in LaCoO3 destabilizes its nonmagnetic low-spin state and generates an anomalous paramagnetic state accompanied by the enhancement of transport gap and magneto-lattice-expansion as well as the contraction of Co─O distance with the increase of electron site transfer. These phenomena are not well described by the mixture of conventional low- and high-spin states, but by their quantum superposition occurring on the verge of a spin-state transition. The present study enables us to significantly accelerate the design of new advanced materials without requiring special equipment, based on the concept of quantum spin-state criticality.

Original languageEnglish
Article number1800057
JournalAdvanced Quantum Technologies
Issue number3
Publication statusPublished - 2018 Dec 1


  • excitonic insulator
  • magneto-lattice-expansion
  • spin-state transition

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Condensed Matter Physics
  • Statistical and Nonlinear Physics
  • Electronic, Optical and Magnetic Materials
  • Computational Theory and Mathematics
  • Mathematical Physics
  • Electrical and Electronic Engineering


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