Superconductivity dichotomy in K-coated single and double unit cell FeSe films on<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>SrTi</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>

Tang, Chunhua; Zhang, Ding; Zang, Yunyi; Liu, Chong; Zhou, Guanyu; Zheng, Liang; Zheng, Cheng; Hu, Xiaopeng; Song, Can-Li; Ji, Shuai‐Hua; Chen, Xi; Wang, Lili; Ma, Xu-Cun; Xue, Qi‐Kun

doi:10.1103/physrevb.92.180507

Cited by 51 publications

(36 citation statements)

References 28 publications

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“…However, it generates a pronounced in-gap bound state at + 4.5 mV (Fig. 3(g) The K atoms appear as single bright dots and contribute somehow charge transfer to monolayer FeSe films [29]. From the measured local density of states on surface K-atom, the superconductivity is basically undisturbed since most of our observation is consistent with previous results [20]: the coherence peaks remain almost unchanged and there is no in-gap bound state.…”

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Extensive impurity-scattering study on the pairing symmetry of monolayer FeSe films onSrTiO3

et al. 2018

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Determination of the pairing symmetry in monolayer FeSe films on SrTiO3 is a requisite for understanding the high superconducting transition temperature in this system, which has attracted intense theoretical and experimental studies but remains controversial. Here, by introducing several types of point defects in FeSe monolayer films, we conduct a systematic investigation on the impurity-induced electronic states by spatially resolved scanning tunneling spectroscopy. Ranging from surface adsorption, chemical substitution to intrinsic structural modification, these defects generate a variety of scattering strength, which renders new insights on the pairing symmetry. IntroductionInterface high temperature superconductivity in monolayer FeSe films grown on SrTiO3 substrates has appealed great interest due to its intriguing interfacial effects and highest superconducting transition temperature (Tc) among iron-based superconductors. It exhibits a characteristic double-full-gap with magnitude of Δ1 ~ 10 meV and Δ2 ~15-20 meV [1][2][3] which closes over 65 K [4,5]. Regardless of the very high transition temperature, its Fermi surface (FS) consists of only electron-like pockets centered around the Brillouin zone (BZ) corners and there are no hole pockets at the BZ center that are typical in bulk iron-based superconductors, as a result of heavy interface electron doping [4][5][6]. The absence of hole pockets at the BZ center directly challenges the previously perceived s± pairing scenario that relies on strong spin fluctuation induced by the repulsive interband interaction between the hole bands around BZ center and the electron bands around BZ corner [7,8].Determination of the pairing symmetry in monolayer FeSe on SrTiO3 is a requisite for understanding the mechanism of high temperature superconductivity. Theoretical studies have proposed various pairing symmetries for such systems with only electron pockets, such as plain s-wave pairing [9][10][11] An experimental pathway to obtain information on pairing symmetry is to study atomic-scale impurity scattering by using scanning tunneling microscopy/spectroscopy (STM/STS) [18,20,21]. It is well known in theory that only magnetic impurities are pair breakers in the plain s-wave superconductors [18], whereas if the pairing order parameter is sign-changing both magnetic and nonmagnetic impurities can induce in-gap states and suppress superconductivity [19]. By introducing surface impurities on the monolayer FeSe surface, earlier STM/STS investigations indicate that the superconductivity is locally suppressed at magnetic impurities (such as Cr and Mn) but remains stubborn at non-magnetic impurities (such as Zn, Ag and K) [20]. Combining the quasi-particle interference patterns and their response to magnetic field, the authors concluded a plain s-wave pairing symmetry in monolayer FeSe on SrTiO3[20].In contrast, recently, Zn substitutional impurities at Fe-site in Li1-xFexOH intercalated FeSe compound, i.e. (Li1-xFex)OHFe1-yZnySe, which has similar FS geometry and a Tc of 40 K...

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Extensive impurity-scattering study on the pairing symmetry of monolayer FeSe films onSrTiO3

et al. 2018

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“…Surprisingly, T c dramatically increases to ∼70K in 1ML FeSe/STO(001) [2]. Charge transfer from STO is widely believed to play an important role in the superconducting mechanism [3], which is supported by doping experiments of bulk or multilayer FeSe [4][5][6][7][8][9]. However, the T c in the doped FeSe systems is less than 50 K, which suggests that there are other substrate related effects contributing to the higher T c in 1ML FeSe/STO(001).…”

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Coexistence of Replica Bands and Superconductivity in FeSe Monolayer Films

et al. 2017

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“…However, at present, there are no experimental results that demonstrate the direct relation between the electron-phonon coupling and the enhancement of the superconductivity. Nevertheless, the interface superconductivity has also been found in related materials such as FeSe on BaTiO 3 [161], Te-doped FeSe on STO [162], KFe 2 Se 2 on STO [148], FeSe on STO(110) [163,164], and FeSe on anatase TiO 2 [165]. In addition, replica bands were also observed in monolayer FeSe on anatase TiO 2 [166].…”

Section: -System MLmentioning

confidence: 92%

“…They also found that the superconducting phase of 3-ML thick films is dome-shaped in a temperature-vs-doping-level phase diagram, suggesting an unconventional mechanism for the superconductivity. Subsequently, the K-adsorption effects were investigated in detail by other several research groups using ARPES [148,149] or STM/STS [150][151][152], and their common results were that the electron-doping can enhance the superconductivity even for a 50-ML-thick FeSe film [149] and the superconducting gap size of the doped samples becomes larger as the thickness becomes thinner, suggesting an interfacial effect for the enhancement of superconductivity in monolayer FeSe.…”

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confidence: 99%

Comparative Review on Thin Film Growth of Iron-Based Superconductors

2017

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Abstract:Since the discovery of the novel iron-based superconductors, both theoretical and experimental studies have been performed intensively. Because iron-based superconductors have a smaller anisotropy than high-T c cuprates and a high superconducting transition temperature, there have been a lot of researchers working on the film fabrication of iron-based superconductors and their application. Accordingly, many novel features have been reported in the films of iron-based superconductors, for example, the fabrication of the epitaxial film with a higher T c than bulk samples, the extraction of the metastable phase which cannot be obtained by the conventional solid state reaction, and so on. In this paper, we review the progress of research on thin film fabrications of iron-based superconductors, especially the four categories: LnFeAs(O,F) (Ln = Lanthanide), AEFe 2 As 2 (AE = Alkaline-earth metal), FeCh (Ch = Chalcogen), and FeSe monolayer. Furthermore, we focus on two important topics in thin films of iron-based superconductors; one is the substrate material for thin film growth on the iron-based superconductors, and the other is the whole phase diagram in FeSe 1−x Te x which can be obtained only by using film-fabrication technique.

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Superconductivity dichotomy in K-coated single and double unit cell FeSe films onSrTiO3

Cited by 51 publications

References 28 publications

Extensive impurity-scattering study on the pairing symmetry of monolayer FeSe films onSrTiO3

Extensive impurity-scattering study on the pairing symmetry of monolayer FeSe films onSrTiO3

Coexistence of Replica Bands and Superconductivity in FeSe Monolayer Films

Comparative Review on Thin Film Growth of Iron-Based Superconductors

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