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arXiv · 1509.08950

Superconductivity dichotomy in K-coated single and double unit cell FeSe films on SrTiO3

Chenjia Tang·Ding Zhang·Yunyi Zang·Chong Liu·Guanyu Zhou·Zheng Li·Cheng Zheng·Xiaopeng Hu·Canli Song·Shuaihua Ji·Ke He·Xi Chen·Lili Wang·Xucun Ma·Qi-Kun Xue
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Abstract

We report the superconductivity evolution of one unit cell (1-UC) and 2-UC FeSe films on SrTiO3(001) substrates with potassium (K) adsorption. By in situ scanning tunneling spectroscopy measurement, we find that the superconductivity in 1-UC FeSe films is continuously suppressed with increasing K coverage, whereas non-superconducting 2-UC FeSe films become superconducting with a gap of ~17 meV or ~11 meV depending on whether the underlying 1-UC films are superconducting or not. This work explicitly reveals that the interface electron-phonon coupling is strongly related to the charge transfer at FeSe/STO interface and plays vital role in enhancing Cooper pairing in both 1-UC and 2-UC FeSe films.

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Chenjia Tang, Ding Zhang, Yunyi Zang, Chong Liu, Guanyu Zhou, Zheng Li, Cheng Zheng, Xiaopeng Hu, Canli Song, Shuaihua Ji, Ke He, Xi Chen, Lili Wang, Xucun Ma, Qi-Kun Xue. 2015-09-29. Superconductivity dichotomy in K-coated single and double unit cell FeSe films on SrTiO3. https://doi.org/10.1103/physrevb.92.180507

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