Lack of coupling between superconductivity and orthorhombic distortion in stoichiometric single-crystalline FeSe

Böhmer, Anna E.; Hardy, F.; Eilers, F.; Ernst, Damien; Adelmann, P.; Schweiß, P.; Wolf, Thomas; Meingast, C.

doi:10.1103/physrevb.87.180505

Cited by 234 publications

(283 citation statements)

References 31 publications

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“…This compound has the simplest crystal structure and stoichiometry while keeping a moderate superconducting critical temperature of about 8 K for polycrystalline samples. 5 Furthermore, high-quality single crystals with rather large dimensions can be grown, [6][7][8] which are necessary for an accurate determination of bulk physical properties. Interestingly, if the tetragonal FeSe system is submitted to a pressure of 8.9 GPa, a huge enhancement of the T c up to 36.7 K is obtained.…”

Section: Introductionmentioning

confidence: 99%

Temperature dependence of lower critical fieldHc1(T)shows nodeless superconductivity in FeSe

Abdel-Hafiez

Vasiliev

et al. 2013

Phys. Rev. B

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We investigate the temperature dependence of the lower critical field H c1 (T ) of a high-quality FeSe single crystal under static magnetic fields H parallel to the c axis. The temperature dependence of the first vortex penetration field has been experimentally obtained by two independent methods and the corresponding H c1 (T ) was deduced by taking into account demagnetization factors. A pronounced change in the H c1 (T) curvature is observed, which is attributed to anisotopic s-wave or multiband superconductivity. The London penetration depth λ ab (T ) calculated from the lower critical field does not follow an exponential behavior at low temperatures, as it would be expected for a fully gapped clean s-wave superconductor. Using either a two-band model with s-wave-like gaps of magnitudes 1 = 0.41 ± 0.1 meV and 2 = 3.33 ± 0.25 meV or a single anisotropic s-wave order parameter, the temperature dependence of the lower critical field H c1 (T ) can be well described. These observations clearly show that the superconducting energy gap in FeSe is nodeless.

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Section: Introductionmentioning

confidence: 99%

Temperature dependence of lower critical fieldHc1(T)shows nodeless superconductivity in FeSe

Abdel-Hafiez

Vasiliev

et al. 2013

Phys. Rev. B

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“…27. Polarized light optical imaging [1,28] was used to characterize the orthorhombic domain pattern appearing below T s as shown in Fig.…”

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confidence: 99%

Origin of the Resistivity Anisotropy in the Nematic Phase of FeSe

et al. 2016

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The in-plane resistivity anisotropy is studied in strain-detwinned single crystals of FeSe. In contrast to other iron-based superconductors, FeSe does not develop long-range magnetic order below the nematic/structural transition at Ts ≈90 K. This allows for the disentanglement of the contributions to the resistivity anisotropy due to nematic and magnetic orders. Comparing direct transport and elastoresistivity measurements, we extract the intrinsic resistivity anisotropy of strainfree samples. The anisotropy peaks slightly below Ts and decreases to nearly zero on cooling down to the superconducting transition. This behavior is consistent with a scenario in which the in-plane resistivity anisotropy in FeSe is dominated by inelastic scattering by anisotropic spin fluctuations.PACS numbers: 74.70. Xa, 74.25.Ld Electronic nematicity has emerged as a key concept in iron-based superconductors since the observation of inplane resistivity anisotropy in stress-detwinned crystals of Co-doped BaFe 2 As 2 [1, 2]. The fact that the resistivity anisotropy is much larger than what is expected from the small lattice distortion led to the proposal that the tetragonal-to-orthorhombic transition in the iron pnictides is driven not by phonons, but by an electronic nematic phase. Subsequent experiments revealed an intricate dependence of the resistivity anisotropy on doping (a sign change between electron-and hole-doped materials [2-6]), and disorder [7,8], sparking hot debates about its microscopic origins (see Refs. [9 and 10] for reviews).Electronic contributions involved in the in-plane resistivity anisotropy [10] can be separated into the Drude weight and/or of the scattering rate anisotropies. Fermisurface anisotropies arising, for instance, from the ferroorbital order triggered at the nematic transition, affect mostly the Drude weight [11][12][13]. Anisotropic scattering, can be due to elastic processes, such as the development of local magnetic order around an impurity [14,15], or inelastic processes, such as the scattering of electrons by anisotropic magnetic fluctuations [16,17] known to exist below T s [18]. Recent stress-dependent optical reflectivity studies in Co-doped BaFe 2 As 2 point to a dominant effect of the Drude weight [19,20]. However, stripe magnetic order appearing at the magnetic transition severely complicates the analysis. This is because the magnetic state breaks tetragonal symmetry leading to an anisotropic reconstruction of the Fermi surface [7,21] and to the appearance of "Dirac cones" [22], which may dramatically alter the resistivity anisotropy [23]. Disentangling these contributions is fundamental to reveal the origin of the resistivity anisotropy and, consequently, of the nematic state.In this context, the stoichiometric FeSe [24] is an ideal system. It is rather clean (residual resistivity ratios as high as 50 [25]) and its orthorhombic/nematic phase transition at T s ≈ 90 K is not accompanied by a longrange magnetic order [26] eliminating effects of Fermi surface folding.In this Letter we rep...

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“…Note that there is a kink around 90 K in the ρ − T curve for annealed FeSe film on LaAlO 3 with large value of RRR ≈ 7. This behavior is familiar in FeSe bulk single crystals, and is due to the structural transition from tetragonal to orthorhombic [197,199]. A structural/nematic transition temperature, T s , for FeSe 1−x Te x films can be estimated from the temperature dependence of the temperature derivative of resistivity shown in Figure 5b as FeSe bulk samples.…”

Section: Comparison In Phase Diagram Between Bulk Single Crystal and mentioning

confidence: 99%

“…Recently, this unique feature of FeSe has attracted lots of attention for exploring the relation between superconductivity and a structural and/or nematic order. Since establishment of the method of growth of FeSe single crystals with high quality [197], many studies on this material have been performed. For investigating this system, it is quite natural to become interested in the substitution effect, for example FeSe 1−x S x and FeSe 1−x Te x .…”

Section: Comparison In Phase Diagram Between Bulk Single Crystal and mentioning

confidence: 99%

“…A structural/nematic transition temperature, T s , for FeSe 1−x Te x films can be estimated from the temperature dependence of the temperature derivative of resistivity shown in Figure 5b as FeSe bulk samples. T s is considered to be a temperature where a temperature derivative of resistivity takes its local minimum (maximum) for FeSe single crystals with large values of RRR [197] (samples with small values of RRR [206,207]). We can define T s at x = 0-0.1 for films on CaF 2 and x = 0-0.3 for films on LAO [133].…”

Section: Comparison In Phase Diagram Between Bulk Single Crystal and mentioning

confidence: 99%

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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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Lack of coupling between superconductivity and orthorhombic distortion in stoichiometric single-crystalline FeSe

Cited by 234 publications

References 31 publications

Temperature dependence of lower critical fieldHc1(T)shows nodeless superconductivity in FeSe

Temperature dependence of lower critical fieldHc1(T)shows nodeless superconductivity in FeSe

Origin of the Resistivity Anisotropy in the Nematic Phase of FeSe

Comparative Review on Thin Film Growth of Iron-Based Superconductors

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