Muon-spin-spectroscopy study of the penetration depth of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>FeTe</mml:mtext></mml:mrow><mml:mrow><mml:mn>0.5</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mtext>Se</mml:mtext></mml:mrow><mml:mrow><mml:mn>0.5</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

Biswas, P. K.; Balakrishnan, G.; Paul, D. McK.; Tomy, C. V.; Lees, Martin R.; Hillier, A. D.

doi:10.1103/physrevb.81.092510

Cited by 56 publications

(54 citation statements)

References 25 publications

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“…The zero temperature values of the energy gaps ∆ I (0) and ∆ II (0) are 2.5 meV (∆ I (0)/k B T c = 1.93) and 1.1 meV (∆ II (0)/k B T c = 0.9), respectively. From the previous measurements, such as µSR 32,33 and penetration depth, 24 two isotropic gaps were reported with gap values similar to our results. µSR studies in FeSe 0.5 Te 0.5 [32 and 33] revealed two gaps of ∆ large ∼ 2.6 meV and ∆ small ∼ 0.5-0.87 meV, and the penetration depth study 24 also showed that ∆ large ∼ 2.1 meV and ∆ s ∼ 1.2 meV.…”

Section: 25supporting

confidence: 79%

Precision global measurements of London penetration depth in FeTe0.58Se0.42

et al. 2011

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We report tunnel diode resonator measurements of in-plane London penetration depth, λ(T ), in optimally-doped single crystals of Fe(Te0.58Se0.42) with Tc ∼ 14.8 K. To avoid any size-dependent calibration effect, six samples of different sizes and deliberately introduced surface roughness were measured and compared. The power-law behavior, ∆λ(T ) = AT n , was found for all samples with the average exponent navg = 2.3 ± 0.1 and the pre-factor Aavg = 1.0 ± 0.2 nm/K 2.3 . The average superfluid density is well described by the self-consistent two-gap γ model resulting in ∆ I (0)/kBTc = 1.93 and ∆ II (0)/kBTc = 0.9. These results suggest the nodeless two-gap pairing symmetry with strong pair breaking effects. In addition, it is found from comparison among six different samples that while the exponent n remains virtually unchanged, the pre-factor A shows some variation, but stays within reasonable margin ruling out some recent suggestions that surface conditions can significantly affect the results. This indicates that the calibration procedure used to obtain λ(T ) from the measured TDR frequency shift is robust and that the uncertainty in sample dimensions and the nature of surface roughness play only a minor role.

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Section: 25supporting

confidence: 79%

Precision global measurements of London penetration depth in FeTe0.58Se0.42

et al. 2011

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“…The two-gap s+s-wave gap model gives a lower χ 2 reduced value than any other above mentioned modelsmodels, and gives a much better fit to the data compared to the single-gap s-wave model with gap values of 8.6(4) and 2.5(3) meV and λ(0) = 289 (22) nm. Therefore it can be concluded that CaKFe 4 As 4 is a multiple gap superconductor which is consistent with other layered Fe-based superconductors [5,[25][26][27]. Some other well-known examples of multi-gap superconductivity are represented by MgB 2 , NbSe 2 , and Lu 2 Fe 3 Si 5 [29][30][31][32].…”

supporting

confidence: 80%

Signature of multigap nodeless superconductivity in CaKFe4As4

et al. 2017

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A newly discovered family of high-Tc Fe-based superconductors, AeAFe4As4 (Ae = Ca, Sr, Eu and A = K, Rb, Cs), offers further opportunities to understand unconventional superconductivity in these materials. In this paper, we report on the superconducting and magnetic properties of CaKFe4As4, studied using muon spectroscopy. Zero field muon-spin-relaxation studies carried out on the CaKFe4As4 superconductor do not show any detectable magnetic anomaly at Tc or below, implying that time-reversal-symmetry is preserved in the superconducting ground state. The temperature dependence of the superfluid density of CaKFe4As4 is found to be compatible with a two-gap s+s-wave model with gap values of 8.6(4) and 2.5(3) meV, similar to the other Fe-based superconductors. The presence of two superconducting energy gaps is consistent with theoretical and other experimental studies on this material. The value of the penetration depth at T = 0 K has been determined as 289 (22) Recent years have witnessed huge research interest in Fe-based superconductors not only due to higher superconducting transition temperature, T c , but also because of the unconventional superconducting properties and interplay with various electronic ground states, such as nematic phase, magnetism [1][2][3][4][5]. This family has a diverse range of structures all containing a common Fe 2 An 2 (An = P, As, Se, Te) layer, analogous to the CuO 2 layers in high-T c cuprates [6]. A e AFe 4 As 4 (A e = Ca, Sr, Eu and A = K, Rb, Cs) materials, discovered in 2016, are the new family of Fe-based superconductors with T c of ≈ 31−36 K [7]. Until now, only a few experimental studies have been performed which show that this new family of superconductors is structurally identical to CaFe 2 As 2 , with the A e and A sites forming alternating planes along the crystallographic c-axis, separated by FeAs layers [7]. Unlike other Fe-based superconductors, A e AFe 4 As 4 does not show any structural phase transition below room temperature [8]. However, Eu-containing A e AFe 4 As 4 show a magnetic transition at ≈ 15 K [9,10]. Along with high T c values, the A e AFe 4 As 4 family also show a very high upper critical field (≈ 92 T for CaKFe 4 As 4 ) [11], similar to the optimally doped (Ba,K)Fe 2 As 2 [12] which is well above the Pauli paramagnetic limit H p (0) = 1.86 * T c for weak-coupling BCS superconductors. Measurements of the London penetration depth λ(T ) using a Tunneldiode resonator (TDR) and tunneling conductance from a Scanning tunneling microscope (STM) spectroscopy show two nodeless gaps in CaKFe 4 As 4 with a larger gap of between 6-9 meV and a smaller gap of between 1-4 meV [13]. High-resolution angle-resolved photoemission spectroscopy (ARPES) measurements and density functional theory (DFT) calculations support multi-band superconductivity in CaKFe 4 As 4 , in which Cooper pairs form in the electron and the hole bands interacting via a dominant interband repulsive interaction enhanced by Fermi surface (FS) nesting [14]. Other thermodynamic and transport measurem...

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“…the sample is always single phase and fully superconducting. The depolarization rate for T > T c is Gaussian and its rather low value, σ N = 0.17µs −1 , indicates that the amount of dilute magnetic impurities, which are often present in IBS and cause an unwanted enhancement in the relaxation rate [105,99], is negligible in that sample. The temperature evolution of the FLL contribution to the depolarization rate, σ SC (T ), and the relative shift of the field at the muon site, (B µ (T ) − H 0 ) /H 0 , due to the diamagnetic shielding are shown in Fig.…”

Section: Transverse-field µ + Sr In Superconducting Materialsmentioning

confidence: 99%

A view from inside iron-based superconductors

Carretta¹,

Renzi²,

Prando³

et al. 2013

Phys. Scr.

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Abstract. Muon spin spectroscopy is one of the most powerful tools to investigate the microscopic properties of superconductors. In this manuscript, an overview on some of the main achievements obtained by this technique in the iron-based superconductors (IBS) are presented. It is shown how the muons allow to probe the whole phase diagram of IBS, from the magnetic to the superconducting phase, and their sensitivity to unravel the modifications of the magnetic and the superconducting order parameters, as the phase diagram is spanned either by charge doping, by an external pressure or by introducing magnetic and non-magnetic impurities. Moreover, it is highlighted that the muons are unique probes for the study of the nanoscopic coexistence between magnetism and superconductivity taking place at the crossover between the two ground-states.

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Muon-spin-spectroscopy study of the penetration depth ofFeTe0.5Se0.5

Cited by 56 publications

References 25 publications

Precision global measurements of London penetration depth in FeTe0.58Se0.42

Precision global measurements of London penetration depth in FeTe0.58Se0.42

Signature of multigap nodeless superconductivity in CaKFe4As4

A view from inside iron-based superconductors

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