Pressure-induced unconventional superconductivity near a quantum critical point in CaFe2As2

Abstract

75As-zero-field nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements are performed on CaFe2As2 under pressure. At P = 4.7 and 10.8 kbar, the temperature dependences of nuclear-spin-lattice relaxation rate (1/T1) measured in the tetragonal phase show no coherence peak just below Tc(P) and decrease with decreasing temperature. The superconductivity is gapless at P = 4.7 kbar but evolves to that with multiple gaps at P = 10.8 kbar. We find that the superconductivity appears near a quantum critical point under pressures in the range 4.7 kbar < P < 10.8 kbar. Both electron correlation and superconductivity disappear in the collapsed tetragonal phase. A systematic study under pressure indicates that electron correlations play a vital role in forming Cooper pairs in this compound.

5pages, 5figures

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• Anomalous Compressibility Effects and Superconductivity in EuFe2As2 under High Pressures
• Antiferromagnetic Spin Fluctuation above the Superconducting Dome and the Full-Gaps Superconducting State in LaFeAsO1-xFx Revealed by 75As-Nuclear Quadrupole Resonance
• Abrupt recovery of Fermi-liquid transport by the c-axis collapse in CaFe2(As1-xPx)2 single crystals
• Superconductivity Induced in Iron Telluride Films by Low Temperature Oxygen Incorporation
• Narrow Bandgap in beta-BaZn2As2 and Its Chemical Origins
• Progressive slowing down of spin fluctuations in underdoped LaFeAsO${}_{1-x}$F${}_x$
• Phase diagram of superconductivity and antiferromagnetism in single crystals of Sr(Fe1-xCox)2As2 and Sr1-yEuy(Fe0.88Co0.12)2As2
• The suppression of electron correlations in the collapsed tetragonal phase of CaFe2As2 under ambient pressure demonstrated by 75As NMR-NQR measurements
• Volovik Effect and Fermi-Liquid Behavior in the s-Wave Superconductor CaPd2As2: 75As NMR-NQR Measurements
• Ferromagnetic cluster-glass phase in Ca(Co,Ir)2As2 crystals
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• Antiferromagnetic spin correlations and pseudogap-like behavior in Ca(Fe1-xCox)2As2 studied by 75As nuclear magnetic resonance and anisotropic resistivity
• Pairing symmetry of superconductivity coexisting with antiferromagnetism
• Magnetism and superconductivity in Sr${}_2$VFeAsO${}_3$ revealed by ${}^{75}$As- and ${}^{51}$V-NMR under elevated pressures
• Quenched Fe Moment in the Collapsed Tetragonal Phase of Ca${}_{1-x}$Pr${}_x$Fe${}_2$As${}_2$
• Magnetic properties of the itinerant A-type antiferromagnet CaCo2P2 studied by 59Co and 31P NMR