75As NMR study of single crystals of the heavily overdoped pnictide superconductors Ba{1-x}KxFe2As2 (x = 0.7 and 1)

Abstract

We performed ${}^{75}$As NMR studies on two overdoped high-quality Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$ (x=0.7 and 1.0) single crystals. In the normal states, we found a dramatic increase of the spin-lattice relaxation ($1{/}^{75}{T}_1$) from the x=0.7 to the x=1.0 samples. In KFe${}_2$As${}_2$, the ratio of $1{/}^{75}{T}_{1}T{K}_n^2$, where ${}^{75}{K}_n$ is the Knight shift, increases as temperature drops. These results indicate the existence of a new type of spin fluctuations in KFe${}_2$As${}_2$ which is accustomed to being treated as a simple Fermi liquid. In the superconducting state, we observe a step-like feature in the temperature dependence of the spin-lattice relaxation of the x=0.7 sample, which supports a two-gap superconductivity as the underdoped materials. However, the temperature scalings of $1{/}^{75}{T}_1$ below Tc in the overdoped samples are significantly different from those in the under or optimal doped ones. A power-law scaling behavior $1{/}^{75}{T}_{1}T\sim T^{0.5}$ is observed, which indicates universal strong low energy excitations in the overdoped hole-type superconductors.

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• Universal heat conduction in the iron-arsenide superconductor KFe2As2 : Evidence of a d-wave state
• Exotic d-wave superconductivity in strongly hole doped K(x)Ba(1-x)Fe2As2
• Universality of superconducting gaps in overdoped Ba0.3K0.7Fe2As2 observed by angle-resolved photoemission spectroscopy
• Pauli-Limited Multiband Superconductivity in KFe2As2
• Incommensurate spin fluctuations in hole-overdoped superconductor KFe2As2
• Possible three dimensional nodes in the $s\pm$ superconducting gap of BaFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$
• 77Se NMR study of pairing symmetry and spin dynamics in KyFe2-xSe2
• The pairing state in KFe2As2 studied by measurements of the magnetic vortex lattice
• Spin fluctuations and unconventional pairing in KFe${}_2$As${}_2$
• Fermi surface in KFe2As2 determined via de Haas-van Alphen oscillation measurements
• Potential antiferromagnetic fluctuations in hole-doped iron-pnictide superconductor Ba_{1-x}K_{x}Fe_{2}As_{2} studied by ^{75}As nuclear magnetic
• Doping dependence of spin fluctuations and electron correlations in iron pnictides
• Evidence of nematic order and nodal superconducting gap along [110] direction in RbFe2As2
• Calorimetric study in single crystal of CsFe${}_2$As${}_2$
• Heat transport in RbFe2As2 single crystal: evidence for nodal superconducting gap
• Crossover in the magnetic response of single-crystalline Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$ and Lifshitz critical point evidenced by Hall effect measurements
• Nodal gap in iron-based superconductor CsFe${}_2$As${}_2$ probed by quasiparticle heat transport
• Nodes in the Order Parameter of Superconducting Iron Pnictides Observed by Infrared Spectroscopy
• Unusual disorder effects in superconducting LaFeAs_(1-d)O_0.9F_0.1 as revealed by NMR spectroscopy
• Microscopic coexistence of superconductivity and antiferromagnetism in underdoped Ba(Fe1-xRux)2As2
• Pseudogap-like phase in Ca(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$ revealed by ${}^{75}$As NQR
• Electronic structure and de Haas-van Alphen frequencies in KFe2As2 within LDA+DMFT
• Nearly-critical spin and charge fluctuations in KFe2As2 observed by high-pressure NMR
• Nanoscale textured superconductivity in Ru-substituted BaFe2As2 : a challenge to a universal phase diagram for the pnictides
• Superconductivity and normal state properties of single-crystalline Tl0.47Rb0.34Fe1.63Se2 as seen via 77Se and 87Rb NMR
• Magnetic fluctuations and superconductivity in Fe pnictides probed by electron spin resonance
• Iron-based superconductors: tales from the nuclei
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• Disordered magnetism in superconducting KFe2As2 single crystals
• Increasing stripe-type fluctuations in $A$Fe${}_2$As${}_2$ ($A$ = K, Rb, Cs) superconductors probed by ${}^{75}$As NMR spectroscopy
• Review of nuclear magnetic resonance studies on iron-based superconductors
• Pairing Symmetry in Iron-Pnictide Superconductor KFe${}_2$As${}_2$
• Anomalous peak effect in iron-based superconductors Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$ ($x\approx$ 0.69 and 0.76) for magnetic-field directions close to the $ab$ plane and its possible relation to the spin paramagnetic effect
• Effects of the vortices and impurities on the nuclear spin relaxation rate in iron-based superconductors
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