Signature of multigap nodeless superconductivity in CaKFe4As4

Abstract

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 Rapid Communication, 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) nm.

5 pages, 4 figures

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• A brief review on muSR studies of unconventional Fe and Cr-based superconductors
• Unique interplay between superconducting and ferromagnetic orders in EuRbFe${}_4$As${}_4$
• Spin Resonance in the New-Structure-Type Iron-Based Superconductor CaKFe4As4
• Analysis of the London penetration depth in Ni-doped CaKFe4As4
• Multigap nodeless superconductivity in CsCa2Fe4As4F2 probed by heat transport
• Time-reversal symmetry breaking and multigap superconductivity in the noncentrosymmetric superconductor La${}_7$Ni${}_3$
• Hedgehog Spin-vortex Crystal Antiferromagnetic Quantum Criticality in CaK(Fe1-xNix)4As4 Revealed by NMR
• Band-selective clean- and dirty-limit superconductivity with nodeless gaps in the bilayer iron-based superconductor CsCa${}_2$Fe${}_4$As${}_4$F${}_2$
• In-plane magnetic penetration depth of superconducting CaKFe${}_4$As${}_4$
• NMR Study of the New Magnetic Superconductor CaK(Fe$0.951Ni0.049)4As4: Microscopic Coexistence of Hedgehog Spin-vortex Crystal and Superconductivity
• High Tc superconductivity in CaKFe${}_4$As${}_4$ in absence of nematic fluctuations
• Multigap superconductivity in RbCa2Fe4As4F2 investigated using muSR measurements
• Robust s+/- pairing in CaK[Fe(1-x)Ni(x)]4As4$ (x = 0 and 0.05) from the response to electron irradiation
• Subdominant $d$-wave interaction in superconducting CaKFe${}_4$As${}_2$?
• Anisotropy induced vortex lattice rearrangement in CaKFe${}_4$As${}_4$
• Whether it is possible to stabilize the 1144-phase pnictides with tri-valence cations?
• Electronic signatures of successive itinerant, magnetic transitions in hexagonal La2Ni7
• Superconductivity of Co-Doped CaKFe4As4 Investigated via Point-Contact Spectroscopy and London Penetration Depth Measurements
• First-principles study of the electronic structure of CaKRu${}_4$P${}_4$