Enhancement of the superconducting gap by nesting in CaKFe4As4 - a new high temperature superconductor

Abstract

We use high resolution angle resolved photoemission spectroscopy and density functional theory with experimentally obtained crystal structure parameters to study the electronic properties of CaKFe4As4. In contrast to related CaFe2As2 compounds, CaKFe4As4 has high Tc of 35K at stochiometric composition. This presents unique opportunity to study properties of high temperature superconductivity of iron arsenic superconductors in absence of doping or substitution. The Fermi surface consists of three hole pockets at $\Gamma$ and two electron pockets at the $M$ point. We find that the values of the superconducting gap are nearly isotropic, but significantly different for each of the FS sheets. Most importantly we find that the overall momentum dependence of the gap magnitudes plotted across the entire Brillouin zone displays a strong deviation from the simple cos(kx)cos(ky) functional form of the gap function, proposed in the scenario of the Cooper-pairing driven by a short range antiferromagnetic exchange interaction. Instead, the maximum value of the gap is observed for FS sheets that are closest to the ideal nesting condition in contrast to the previous observations in some other ferropnictides. These results provide strong support for the multiband character of superconductivity in CaKFe4As4, in which Cooper pairing forms on the electron and the hole bands interacting via dominant interband repulsive interaction, enhanced by FS nesting}.

5 pages, 4 figures

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Cited by in corpus (45)

• Hedgehog spin-vortex crystal stabilized in a hole-doped iron-based superconductor
• Ultra-high critical current densities, the vortex phase diagram and the effect of granularity of the stoichiometric high-Tc superconductor, CaKFe${}_4$As${}_4$
• Large and significantly anisotropic critical current density induced by planar defects in CaKFe4As4 single crystals
• Influence of the multiband sign changing superconductivity on the vortex cores and on vortex pinning in the new stoichiometric high Tc CaKFe4As4
• Magnetic fluctuations and superconducting properties of CaKFe4As4 studied by 75As NMR
• Nodal multigap superconductivity in KCa${}_2$Fe${}_4$As${}_4$F${}_2$
• Two-gap superconductivity with line nodes in CsCa${}_2$Fe${}_4$As${}_4$F${}_2$
• Odd and even modes of neutron spin resonance in the bilayer iron-based superconductor CaKFe${}_4$As${}_4$
• Pairing Mechanism in Hunds Metal Superconductors and the Universality of the Superconducting Gap to Critical Temperature Ratio
• Signature of multigap nodeless superconductivity in CaKFe4As4
• Spectroscopic Evidence of Bilayer Splitting and Interlayer Pairing in an Iron Based Superconductor
• Electronic properties, low-energy Hamiltonian and superconducting instabilities in CaKFe${}_4$As${}_4$
• Competing pairing interactions responsible for the large upper critical field in a stoichiometric iron-based superconductor, CaKFe${}_4$As${}_4$
• A brief review on muSR studies of unconventional Fe and Cr-based superconductors
• Spin Resonance in the New-Structure-Type Iron-Based Superconductor CaKFe4As4
• When superconductivity does not fear magnetism: Insight into electronic structure of RbEuFe${}_4$As${}_4$
• Analysis of the London penetration depth in Ni-doped CaKFe4As4
• Multigap nodeless superconductivity in CsCa2Fe4As4F2 probed by heat transport
• Hedgehog Spin-vortex Crystal Antiferromagnetic Quantum Criticality in CaK(Fe1-xNix)4As4 Revealed by NMR
• Single particle tunneling spectroscopy and superconducting gaps in layered iron based superconductor KCa${}_2$Fe${}_4$As${}_4$F${}_2$
• 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${}_4$
• Multigap superconductivity in RbCa2Fe4As4F2 investigated using muSR measurements
• High Tc superconductivity in CaKFe${}_4$As${}_4$ in absence of nematic fluctuations
• NMR Study of the New Magnetic Superconductor CaK(Fe$0.951Ni0.049)4As4: Microscopic Coexistence of Hedgehog Spin-vortex Crystal and Superconductivity
• Effect of gap anisotropy on the spin resonance peak in the superconducting state of iron-based materials
• Anisotropic upper critical field of pristine and proton-irradiated single crystals of the magnetically ordered superconductor RbEuFe${}_4$As${}_4$
• Subdominant $d$-wave interaction in superconducting CaKFe${}_4$As${}_2$?
• Pressure-temperature phase diagrams of CaK(Fe${}_{1-x}$Ni${}_x$)${}_4$As${}_4$ superconductors
• Anisotropy induced vortex lattice rearrangement in CaKFe${}_4$As${}_4$
• Observation of Two Collapsed Phases in CaRbFe4As4
• Structural, electronic, and dynamical properties of the tetragonal and collapsed tetragonal phases of KFe${}_2$As${}_2$
• Fluctuations and pairing in Fe-based superconductors: Light scattering experiments
• Whether it is possible to stabilize the 1144-phase pnictides with tri-valence cations?
• Multi-band description of the upper critical field of bulk FeSe
• Prediction of Double-Weyl Points in the Iron-Based Superconductor CaKFe${}_4$As${}_4$
• Common ($\pi$,$\pi$) Band Folding and Surface Reconstruction in FeAs-Based Superconductors
• Slope of the upper critical field at $T_c$ in two-band superconductors with non-magnetic disorder: $s_{++}$ superconductivity in ${\text{Ba}}_{1-x}{\text{K}}_x{\text{Fe}}_2{\text{As}}_2$
• Anomalous metallic oxygen band in the potential superconductor KCa${}_2$Fe${}_4$As${}_4$O${}_2$
• Evolution of Critical Current Density in CaKFe${}_4$As${}_4$ with La-doping
• Electronic signatures of successive itinerant, magnetic transitions in hexagonal La2Ni7
• Pressure-temperature phase diagram of CaK(Fe${}_{1-x}$Mn${}_x$)${}_4$As${}_4$ for $x$=0.024
• Superconductivity of Co-Doped CaKFe4As4 Investigated via Point-Contact Spectroscopy and London Penetration Depth Measurements
• Anisotropic superconductivity and Fermi surface reconstruction in the spin-vortex antiferromagnetic superconductor CaK(Fe${}_{0.95}$Ni${}_{0.05}$)${}_4$As${}_4$
• First-principles study of the electronic structure of CaKRu${}_4$P${}_4$