Carrier doping effect of excitonic insulator candidate TaNiSe, 4

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

Exciton 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 are beginning 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. Furthermore, when titanium is substituted for tantalum (M = Ti), the electrical resistivity of the sample with composition ratio x less than 0.06 is semiconducting, while the electrical resistivity of the high-temperature phase behaves metallic when x = 0.06 or higher. The phase transition shown in this study may be a new insight into the realization of excitonic insulators.