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arXiv · 2308.15722

Checkerboard order state in superconducting FeSe/SrTiO3(001) monolayer

Cheng-Long Xue·Qian-Qian Yuan·Yong-Jie Xu·Qi-Yuan Li·Li-Guo Dou·Zhen-Yu Jia·Shao-Chun Li
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Abstract

Ordered electronic states have been extensively explored in cuprates and iron-based unconventional superconductors, but seldom observed in the epitaxial FeSe/SrTiO3(001) monolayer (FeSe/STO) with an enhanced superconducting transition temperature (Tc). Here, by using scanning tunneling microscopy/ spectroscopy (STM/STS), we reveal a checkerboard charge order in the epitaxial FeSe/STO monolayer, with a period of four times the inter-Fe-atom distance along two perpendicular directions of the Fe lattice. This ordered state is uniquely present in the superconducting FeSe/STO monolayer, even at liquid nitrogen temperature, but absent in the non-superconducting FeSe monolayer or bilayer. Quasiparticle interference (QPI) measurements further confirm it as a static order without an energy-dependent dispersion and gapped out within the superconductivity gap. The intensity of the charge order shows an enhancement near the superconducting transition temperature, thus implying a correlation with the high-Tc superconductivity in the FeSe/STO monolayer. This study provides a new basis for exploring the ordered electronic states and their interplay with high-Tc superconductivity in the FeSe monolayer.

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Cheng-Long Xue, Qian-Qian Yuan, Yong-Jie Xu, Qi-Yuan Li, Li-Guo Dou, Zhen-Yu Jia, Shao-Chun Li. 2023-08-30. Checkerboard order state in superconducting FeSe/SrTiO3(001) monolayer. https://doi.org/10.1103/physrevb.107.134516

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