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Interface-induced superconductivity and strain-dependent spin density waves in FeSe/SrTiO3 thin films


The record superconducting transition temperature (Tc) for the iron-based high-temperature superconductors (Fe-HTS) has long been 56 K. Recently, in single-layer FeSe films grown on SrTiO3 substrates, indications of a new record of 65 K have been reported. Using in situ photoemission measurements, we substantiate the presence of spin density waves (SDWs) in FeSe films—a key ingredient of Fe-HTS that was missed in FeSe before—and we find that this weakens with increased thickness or reduced strain. We demonstrate that the superconductivity occurs when the electrons transferred from the oxygen-vacant substrate suppress the otherwise pronounced SDWs in single-layer FeSe. Beyond providing a comprehensive understanding of FeSe films and directions to further enhance its Tc, we map out the phase diagram of FeSe as a function of lattice constant, which contains all the essential physics of Fe-HTS. With the simplest structure, cleanest composition and single tuning parameter, monolayer FeSe is an ideal system for testing theories of Fe-HTS.

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Figure 1: The electronic structure of FeSe films as a function of thickness.
Figure 2: Electronic structure evolution during the growth of 1 ML FeSe.
Figure 3: Temperature dependence of the electronic structure for the 50 ML FeSe film.
Figure 4: Thickness dependence of the SDW behaviour for the multi-layer FeSe films.
Figure 5: Phase diagram of FeSe.


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We gratefully acknowledge Q. Xue, X. Chen and W. Li for sharing their thin film growth procedures, Z. Lu for the file of the FeSe band structure, Y. Zhang and F. Yang for AFM characterization of the STO substrate, and enlightening discussions with C. Varma. This work is supported in part by the National Science Foundation of China, and the National Basic Research Program of China (973 Program) under the grant Nos. 2012CB921400,2011CB921802, 2011CBA00112, 2011CB309703, 91026016.

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Authors and Affiliations



S.T., M.X., X.X., D.X., H.X. and R.P. built the MBE system and grew the films, S.T., Y.Z., Z.Y., F.C., Q.F., J.J. and B.X. performed ARPES measurements. S.T., D.F., Y.Z., Z.Y., T.Z., T.X. and J.H. analysed the ARPES data. D.F. wrote the paper. D.F. and X.L. are responsible for the infrastructure, project direction and planning.

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Correspondence to Donglai Feng.

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Tan, S., Zhang, Y., Xia, M. et al. Interface-induced superconductivity and strain-dependent spin density waves in FeSe/SrTiO3 thin films. Nature Mater 12, 634–640 (2013).

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