Iron Vacancy Tunable Superconductor-Insulator Transition in FeSe/SrTiO3 Monolayer
Cheng-Long Xue, Li-Guo Dou, Yong-Jie Xu, Qian-Qian Yuan, Qi-Yuan Li, Zhen-Yu Jia, Zishuang Li, Ronghua Liu, Shao-Chun Li
DOI 10.1103/PhysRevLett.131.256002 · Physical Review Letters
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Abstract
The Fe4Se5 with a 5×5 Fe vacancy order is suggested to be a Mott insulator and the parent state of bulk FeSe superconductor. The iron vacancy ordered state has been considered as a Mott insulator and the parent compound of bulk FeSe-based superconductors. However, for the superconducting FeSe/SrTiO3 monolayer (FeSe/STO) with an interface-enhanced high transition temperature (Tc), the electronic evolution from its Fe vacancy ordered parent phase to the superconducting state, has not been explored due to the challenge to realize an Fe vacancy order in the FeSe/STO monolayer, even though important to the understanding of superconductivity mechanism. In this study, we developed a new method to generate Fe vacancies within the FeSe/STO monolayer in a tunable fashion, with the assistance of atomic hydrogen. As a consequence, an insulating 5×5 Fe vacancy ordered monolayer is realized as the parent state. By using scanning tunneling microscopy and scanning tunneling spectroscopy, the spectral evolution from superconductivity to insulator is fully characterized. Surprisingly, a prominent spectral weight transfer occurs, thus implying a strong electron correlation effect. Moreover, the Fe vacancy induced insulating gap exhibits no Mott gap-like features. This work provides new insights in understanding the high-Tc superconductivity in FeSe/STO monolayer.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| FeSe Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 8 | Pressure not reported | unknown |
| FeSe Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | — | Pressure not reported | unknown |
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