励起子絶縁体候補物質TaNiSeのTi, Hf置換試料の圧力効果

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土田 駿*; 広瀬 雄介*; 関川 卓也; 大野 義章*; 摂待 力生*

Tsuchida, Shun*; Hirose, Yusuke*; Sekikawa, Takuya; Ono, Yoshiaki*; Settai, Rikio*

励起子絶縁体は、結晶中で電子と正孔が結合し、それらが集団的に振る舞うことで結晶全体が絶縁体化する性質を有し、新規物性として注目され始めた。本研究では、励起子絶縁体の候補物質の一つであるが合成自体が困難で物性解明が進んでいないTaNiSeに着目し、まずキャリアドープを目的とした元素置換試料(TaM)NiSe(M = Ti, Hf)の育成を行い、圧力効果を調べた。結果、(TaM)NiSeはx=0.08の試料の高圧領域で超伝導が観測された。超伝導転移温度は圧力の増加に伴い上昇することが明らかになった。本研究で示した相転移は、励起子絶縁体と超伝導の関係に関する新たな知見となりうる。

The excitonic insulators have the property that the entire crystal becomes an insulator due to the collective behavior of electrons and holes bound together in the crystal, and they have begun to attract attention as a new physical property. In this study, we focused on TaNiSe, which is one of the excitonic insulator candidates, but its synthesis itself is difficult and its physical properties have not yet been clarified. As a result, superconductivity was observed in (TaM)NiSe at x = 0.08 in the high pressure region. The superconducting transition temperature was found to increase with increasing pressure. The phase transition shown in this study may provide new insight into the relationship between exciton insulators and superconductivity.