${}^{75}$As NMR of Ba(Fe${}_{0.93}$Co${}_{0.07}$)${}_2$As${}_2$ in High Magnetic Field

Abstract

The superconducting state of an optimally doped single crystal of Ba(Fe${}_{0.93}$Co${}_{0.07}$)${}_2$As${}_2$ was investigated by ${}^{75}$As NMR in high magnetic fields from 6.4 T to 28 T. It was found that the Knight shift is least affected by vortex supercurrents in high magnetic fields, $H>11$ T, revealing slow, possibly higher order than linear, increase with temperature at $T\lesssim 0.5T_c$, with $T_c\approx 23K$. This is consistent with the extended s-wave state with $A_{1g}$ symmetry but the precise details of the gap structure are harder to resolve. Measurements of the NMR spin-spin relaxation time, $T_2$, indicate a strong indirect exchange interaction at all temperatures. Below the superconducting transition temperature vortex dynamics lead to an anomalous dip in $T_2$ at the vortex freezing transition from which we obtain the vortex phase diagram up to $H=28$ T.

13 pages, 9 figures

References in corpus (32)

• Unconventional pairing originating from disconnected Fermi surfaces in superconducting LaFeAsO${}_{1-x}$F${}_x$}
• Observation of Fermi-surface-dependent nodeless superconducting gaps in Ba0.6K0.4Fe2As2
• Near-degeneracy of several pairing channels in multiorbital models for the Fe-pnictides
• Magnetism, superconductivity, and pairing symmetry in Fe-based superconductors
• Effects of Co substitution on thermodynamic and transport properties and anisotropic $H_{c2}$ in Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$ single crystals
• Funtional Renormalization Group Study of the Pairing Symmetry and Pairing Mechanism of the FeAs Based High Temperature Superconductors
• Pairing Symmetry in a Two-Orbital Exchange Coupling Model of Oxypnictides
• Small anisotropy, weak thermal fluctuations, and high field superconductivity in Co-doped iron pnictide Ba(Fe1-xCox)2As2
• Vortex phase diagram of Ba(Fe0.93Co0.07)2As2 single crystals
• Scanning Tunneling Spectroscopy and Vortex Imaging in the Iron-Pnictide Superconductor BaFe${}_{1.8}$Co${}_{0.2}$As${}_2$
• Commensurate Itinerant Antiferromagnetism in BaFe2As2: 75As-NMR Studies on a Self-Flux Grown Single Crystal
• Spin fluctuations and superconductivity in a 3D tight-binding model for BaFe2As2
• Evidence for nodal superconductivity in LaFePO
• Spin susceptibility, phase diagram, and quantum criticality in the electron-doped high Tc Superconductor Ba[Fe(1-x)Co(x)]2As2
• Low temperature specific heat of the hole-doped Ba_{0.6}K_{0.4}Fe_2As_2 single crystals and electron-doped SmFeAsO_{0.9}F_{0.1} samples
• Fully Gapped Superconducting State Based on a High Normal State Quasiparticle Density of States in Ba${}_{0.6}$K${}_{0.4}$Fe${}_2$As${}_2$ Single Crystals
• Unconventional London penetration depth in Ba(Fe0.93Co0.07)2As2 single crystals
• Momentum dependence and nodes of the superconducting gap in iron-pnictides
• Origin of Gap Anisotropy in Spin Fluctuation Models of the Fe-pnictides
• Evidence for two-gap superconductivity in (Ba,K)Fe_2As_2 by directional point contact Andreev reflection spectroscopy
• Local measurement of the superfluid density in the pnictide superconductor Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$ across the superconducting dome
• A doping dependent specific heat study of the superconducting gap in Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$
• Pinpointing Gap Minima in Ba(Fe${}_{0.94}$Co${}_{0.06}{)}_2$As${}_2$ \textit{via} Band Structure Calculations and Electronic Raman Scattering
• Effect of annealing on the specific heat of Ba(Fe1-xCox)2As2
• Vortex studies in superconducting Ba(Fe0.93Co0.07)2As2
• Two-dimensional Vortices in Superconductors
• Superfluid Density and Field-Induced Magnetism in Ba(Fe1-xCox)2As2 and Sr(Fe1-xCox)2As2 Measured with Muon Spin Relaxation
• Optical signature of sub-gap absorption in the superconducting state of Ba(Fe,Co)2As2
• Nodes vs. minima in the energy gap of iron-pnictides from field-induced anisotropy
• Angular resolved specific heat in iron-based superconductors: the case for nodeless extended $s$-wave gap
• Calorimetric Evidence for Nodes in the Overdoped Ba(Fe${}_{0.9}$Co${}_{0.1}$)${}_2$As${}_2$
• Large $D-2$ Theory of Superconducting Fluctuations in a Magnetic Field and its Application to Iron-Pnictides

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