Evidence of Mott insulator with thermally induced melting behavior in kagome compound Nb3Cl8

Qiu Yang; Min Wu; Jingyi Duan; Zhijie Ma; Lingxiao Li; Zihao Huo; Zaizhe Zhang; Kenji Watanabe; Takashi Taniguchi; Xiaoxu Zhao; Yi Chen; Youguo Shi; Wei Jiang; Kaihui Liu; Xiaobo Lu

doi:10.1093/nsr/nwaf464

Article Evidence of Mott insulator with thermally induced melting behavior in kagome compound Nb3Cl8

Qiu Yang ; Min Wu ; Jingyi Duan ; Zhijie Ma ; Lingxiao Li ; Zihao Huo ; Zaizhe Zhang ; Kenji Watanabe (National Institute for Materials Science) ; Takashi Taniguchi (National Institute for Materials Science) ; Xiaoxu Zhao ; Yi Chen ; Youguo Shi ; Wei Jiang ; Kaihui Liu ; Xiaobo Lu

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Qiu Yang, Min Wu, Jingyi Duan, Zhijie Ma, Lingxiao Li, Zihao Huo, Zaizhe Zhang, Kenji Watanabe, Takashi Taniguchi, Xiaoxu Zhao, Yi Chen, Youguo Shi, Wei Jiang, Kaihui Liu, Xiaobo Lu. Evidence of Mott insulator with thermally induced melting behavior in kagome compound Nb3Cl8. National Science Review. 2025, 12 (12), nwaf464. https://doi.org/10.1093/nsr/nwaf464

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The kagome lattice provides a playground to explore novel correlated quantum states due to the presence of flat bands in its electronic structure. Recently discovered layered kagome compound Nb3Cl8 has been proposed as a Mott insulator coming from the half-filled flat band. Here we have carried out systematic transport study to uncover the evidence of Mott insulator in Nb3Cl8 thin flakes. Bipolar semiconducting property with Fermi level close to conduction band has been revealed. We have further probed the chemical potential of Nb3Cl8 by tracing the charge neutrality point of the monolayer graphene proximate to Nb3Cl8. The gap of Nb3Cl8 flakes is approximately 𝟏. 𝟏𝟎 𝐞𝐕 at 𝟏𝟎𝟎 𝐊 and shows pronounced temperature dependence, decreasing substantially with increasing temperature to ~𝟎. 𝟔𝟑 𝐞𝐕 at 𝟑𝟎𝟎 𝐊 . The melting behavior of the gapped state is in consistent with theoretically proposed Mott insulator in Nb3Cl8. Our work has demonstrated Nb3Cl8 as a promising platform to study strongly correlated physics at relatively high temperature.

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