結晶の化学組成などを適切に制御すると、量子相転移と呼ばれる絶対零度での相転移が起こることがあります。一般に、この相転移点は量子臨界点と呼ばれます。
A typical phase transition exhibited by crystalline solids involves a change in the crystal structure. Such structural phase transitions usually occur at finite temperatures. However, controlling the chemical composition of the crystal can lower the transition temperature to absolute zero temperature(−273°C). The transition point at absolute zero is called the structural quantum critical point (sQCP).
構造量子臨界点では、結晶構造の一部が自発的に非周期化し、ガラス状の非周期構造と結晶の周期構造が組み合わさった特殊な構造となっていることを、本研究によって初めて明らかにしました。
We have discovered for the first time that a part of the atomic structure loses periodicity because of the incoherently frozen acoustic soft mode at the sQCP. As a result, a combination of a glassy aperiodic structure and a periodic atomic arrangement is realized (sublattice glass).
一般の方向けの解説記事：プレスリリース「構造量子臨界点付近の結晶質固体Ba1-xSrxAl2O4が結晶・非晶質両方の性質を併せ持つことを発見」
専門家の方向けの解説記事：日本物理学会誌 2023年12月号 「最近の研究から」(概要)
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構造量子臨界点近傍で強まっている構造揺らぎが、超伝導の新しい"糊"となっている可能性を見出しました。現在、様々な物質に対象を広げ、その特徴を調べています。
Our group is leading the research elucidating the essence of structural quantum critical phenomena. We are now expanding the scope of our research to various materials and investigating their characteristics widely.
Superionic conductors have recently attracted renewed attention for their use as thermoelectric materials due to their extremely low lattice thermal conductivity. Of central interest is why the superionic conductors exhibit such low thermal conductivity and competing mechanisms have been proposed thus far.
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