Novel quantum properties and lattice dynamics caused by suppression of ferroelectricity

2022 Fiscal Year Final Research Report

• Project/Area Number: 20H01844
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 13020:Semiconductors, optical properties of condensed matter and atomic physics-related
• Research Institution: Osaka Metropolitan University (2022); Osaka Prefecture University (2020-2021)
• Principal Investigator: Ishii Yui 大阪公立大学, 大学院工学研究科, 准教授 (50708013)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 構造量子臨界点 / ソフトモード

Outline of Final Research Achievements

In this project, we have revealed that a “sublattice glass state” appears at the structural quantum critical point where an acoustic-phonon-driven structural phase transition is suppressed down to the absolute zero temperature. This state possesses both crystalline periodicity and glasslike atomic arrangement. As a result of the glasslike atomic arrangement, the lattice-specific heat shows an excess approximately at 10 K and a T-linear term at the lowest temperatures, and the thermal conductivity shows a plateau, all of which are the typical characteristics of amorphous solids. In addition, it was found that the atomic vibrational state of this state resembles that amorphous solids typically exhibit.

Free Research Field

固体化学

Academic Significance and Societal Importance of the Research Achievements

量子臨界点の研究はこれまで磁気秩序などスピンのかかわる秩序相を対象として発展し、それに隣接して現れる新奇量子相の研究は、今日に至るまで物性物理学の一大分野を築いている。しかしながら、スピンと並びフォノンも固体中の基本的な量子の1つであるにもかかわらず、フォノンが主役となって現れる量子臨界点の研究はほとんど進んで来なかった。本研究で得られた成果は、従来のスピン主体の量子臨界研究をフォノン系に展開するための足がかりとなると期待できる。