Search of new strongly correlated quasicrystals

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K05524
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Condensed matter physics II
• Research Institution: Toyota Physical and Chemical Research Institute
• Principal Investigator: Ishimasa Tsutomu 公益財団法人豊田理化学研究所, フェロー事業部門, フェロー (10135270)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 準結晶 / 価数揺動 / 量子臨界 / 希土類合金 / 近似結晶

Outline of Final Research Achievements

Quasicrystals are a group of materials with a special long-range order (quasiperiodicity) showing diffraction symmetry different from ordinal crystals such as icosahedral symmetry and 12-fold symmetry. In order to clarify the physical properties originated from such structural specificity, we have conducted research centered on new-substance search. Theoretically, the possibility of a new dodecagonal quasicrystal containing Yb was pointed out using "high-dimensional analysis", and experimentally the first superconductivity (Zn-Mg-Al alloy) in a quasicrystal as well as formation of a new quasicrystal in Zn-Au alloys were discovered. Furthermore, we found phase separation (Cu-Ga-Sc alloy) with a difference in cluster structure, and a difference in electronic state of Yb (Au-Ge-Yb alloy) due to similar difference in the approximant crystals.
It is thought that these have brought us one step closer to the goal of “clarifying the physical properties inherent in quasicrystals”.

Free Research Field

固体物理学

Academic Significance and Societal Importance of the Research Achievements

歴史の区分として，しばしば石器時代，青銅時代，鉄器時代，シリコン時代などを用いますが，これらは全て”結晶の時代”と言うことができます．ところが最近，専門家の間では準結晶と呼ばれる物質群が注目されています．準結晶は，アルミニウム，銅，鉄など，金属の合金として形成しますが，結晶ともアモルファスとも異なる「特別の規則」に従って原子が並んでいるため，従来の金属材料とは異なる「未来材料になりうるような性質」を持っています．ここでは，新物質探索を軸として，そのような準結晶についての基礎研究を行いました．