Measurements of the superconducting anisotropy in FeSe with a resonance frequency technique

Cao, Rongxing; Dong, Jun; Wang, Q. L.; Yang, Yanjun; Zhao, Chihang; Zeng, Xianghua; Чареев, Д. А.; Vasiliev, A. N.; Wu, Bing; Wu, Guoqing

doi:10.1063/1.5093591

Cited by 7 publications

(5 citation statements)

References 57 publications

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“…Figure 9 shows the variations of ξ c (0) and d with Ag content in the FeSe samples as determined from the FIC analysis. The coherence length for the pure FeSe sample determined here compares well to the data published in [40,41] for FeSe single crystals (ξ c (0) = 2.9 nm). Therefore, we see that the Ag addition to FeSe reduces ξ c (0) and consequently enhances also B c (0) and B c2 (0), which is an additional benefit.…”

Section: T 1d-sw T 2d-1d T 3d-2d T Cr-3d T Csupporting

confidence: 83%

Section: T 1d-sw T 2d-1d T 3d-2d T Cr-3d T Cmentioning

confidence: 99%

“…x % Ag In [40,41], the anisotropy parameter, γ, was determined to be 2.4 for FeSe. Taking this value, we find ξ ab (0) = 6.04 nm for the pure FeSe samples, which compares well to the 5.2 nm found in [40]. The values for the thermodynamic critical field, B c (0), obtained here are reasonable for polycrystalline HTSc samples.…”

Section: T 1d-sw T 2d-1d T 3d-2d T Cr-3d T Cmentioning

confidence: 99%

“…The B c2 (0) data were obtained from Equations ( 6)-( 9), which are based on the Werthamer-Helfand-Hohenberg (WHH) theory [42]. In [40], the fits to the data obtained with a resonance frequency technique led also to values above 40 T for B c2 (0). Regarding the spin-paramagnetic effect, much smaller values for B c2 (0) of about 12 T (H c) and 29 T (H ⊥ c) were obtained, which fit much better to other published measurements and to values obtained on other IBS materials.…”

Section: T 1d-sw T 2d-1d T 3d-2d T Cr-3d T Cmentioning

confidence: 99%

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Excess Conductivity Analysis of Polycrystalline FeSe Samples with the Addition of Ag

et al. 2020

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Bulk FeSe superconductors of the iron-based (IBS) “11” family containing various additions of silver were thoroughly investigated concerning the microstructure using optical microscopy and electron microscopy (TEM and SEM). The measurements of electrical resistivity were performed through the four-point technique in the temperature interval T= 2–150 K. The Aslamazov–Larkin model was employed to analyze the fluctuation-induced conductivity (FIC) in all acquired measurements. In all studied products, we found that the FIC curves consist of five different regimes of fluctuation, viz. critical region (CR), three-dimensional (3D), two-dimensional (2D), one-dimensional (1D), and shortwave fluctuation (SWF) regimes. The critical current density (Jc), the lower and upper critical magnetic fields (Bc1 and Bc2), the coherence length along the c-axis at zero-temperature (ξc(0)), and further parameters were assessed with regards to the silver amount within the products. The analyses discloses a diminution in the resistivity and a great reduction in ξc(0) with Ag addition. The optimal silver doping amount is achieved for 7 wt.%, which yields the best superconducting transition and the greatest Jc value.

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Section: T 1d-sw T 2d-1d T 3d-2d T Cr-3d T Csupporting

confidence: 83%

Section: T 1d-sw T 2d-1d T 3d-2d T Cr-3d T Cmentioning

confidence: 99%

Section: T 1d-sw T 2d-1d T 3d-2d T Cr-3d T Cmentioning

confidence: 99%

Section: T 1d-sw T 2d-1d T 3d-2d T Cr-3d T Cmentioning

confidence: 99%

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Excess Conductivity Analysis of Polycrystalline FeSe Samples with the Addition of Ag

et al. 2020

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“…That T orb is linearly proportional to B 0 could be understood due to its full magnetic character that involves electron orbital moments, while the reason for the suppression of T orb by B 0 is not clear. The suppression of T c by B 0 is mainly due to the spin-paramagnetic effect in the vortex lattice as we recently reported [50].…”

supporting

confidence: 67%

Observation of orbital ordering and origin of the nematic order in FeSe

Cao

Dong

et al. 2019

New J. Phys.

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In iron-based superconductors the interactions driving the nematic order that breaks the lattice fourfold rotational symmetry in the iron plane may also facilitate the Cooper pairing, but experimental determination of these interactions is challenging because the temperatures of the nematic order and the order of other electronic phases appear to match each other or to be close to each other. Here we performed field-dependent 77 Se-nuclear magnetic resonance (NMR) measurements on single crystals of iron-based superconductor FeSe, with magnetic field B 0 up to 16 T. The 77 Se-NMR spectra and Knight shift split when the direction of B 0 is away from the direction perpendicular to the iron planes (i.e. B 0 Pc) upon cooling in temperature, with a significant change in the distribution and magnitude of the internal magnetic field at the 77 Se nucleus, but these do not happen when B 0 is perpendicular to the iron planes, thus demonstrating that there is an orbital ordering. Moreover, stripe-type antiferromagnetism is absent, while giant antiferromagnetic spin fluctuations measured by the NMR spin-lattice relaxation gradually developed starting at ∼40 K, which is far below the nematic order temperature T nem =89 K. These results provide direct evidence of orbital-driven nematic order in FeSe.

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Magnetic phases in superconducting, polycrystalline bulk FeSe samples

et al. 2021

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The FeSe compound is the simplest high-temperature superconductor (HTSc) possible, and relatively cheap, not containing any rare-earth material. Although the transition temperature, Tc, is just below 10 K, the upper critical fields are comparable with other HTSc. Preparing FeSe using solid-state sintering yields samples exhibiting strong ferromagnetic hysteresis loops (MHLs), and the superconducting contribution is only visible after subtracting MHLs from above Tc. Due to the complicated phase diagram, the samples are a mixture of several phases, the superconducting β-FeSe, and the non-superconducting δ-FeSe and γ-FeSe. Furthermore, antiferromagnetic Fe7Se8 and ferromagnetic α-Fe may be contained, depending directly on the Se loss during the sintering process. Here, we show MHLs measured up to ±7 T and determine the magnetic characteristics, together with the amount of superconductivity determined from M(T) measurements. We also performed a thorough analysis of the microstructures in order to establish a relation between microstructure and the resulting sample properties.

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Measurements of the superconducting anisotropy in FeSe with a resonance frequency technique

Cited by 7 publications

References 57 publications

Excess Conductivity Analysis of Polycrystalline FeSe Samples with the Addition of Ag

Excess Conductivity Analysis of Polycrystalline FeSe Samples with the Addition of Ag

Observation of orbital ordering and origin of the nematic order in FeSe

Magnetic phases in superconducting, polycrystalline bulk FeSe samples

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