Three-dimensional nodal superconducting gap in single crystals Ba(Fe${}_{1-x}$Ni${}_x$)${}_2$As${}_2$

Abstract

The London penetration depth, $\lambda$, is directly related to the density, $n_s$, of the Cooper pairs (${\lambda }^2\propto 1/n_s$) and its variation with temperature provides valuable insight into the pairing mechanism. Here we study the evolution with doping of the temperature dependence of the in-plane (${\lambda }_{ab}$) and out-of-plane (${\lambda }_c$) penetration depths in single crystals of electron-doped Ba(Fe${}_{1-x}$Ni${}_x$)${}_2$As${}_2$. As is the case for other pnictides, $\lambda (T)\sim T^n$ over the whole doping range and this behavior extends down to at least $T=T_c/100$, setting a very small upper limit on the gap minimum. Furthermore, in the overdoped regime: 1) the exponent $n$ becomes substantially smaller than 2, which is incompatible with the models that explain power-law behavior to be due to scattering; 2) the exponent $n$ becomes anisotropic, with ${\lambda }_c(T)$ showing a clear $T$-linear behavior over a large temperature interval. These findings suggest that in the overdoped regime the superconducting gap in iron-based pnictide superconductors develops nodal structure, which unlike in the cuprates, cannot be understood within a two-dimensional picture.

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Cited by in corpus (35)

• Superconductivity in Iron Compounds
• Gap symmetry and structure of Fe-based superconductors
• Orbital Fluctuation Mediated Superconductivity in Iron Pnictides: Analysis of Five Orbital Hubbard-Holstein Model
• Spin fluctuations and superconductivity in a 3D tight-binding model for BaFe2As2
• London Penetration Depth in Iron - based Superconductors
• Nodes in the gap structure of the iron-arsenide superconductor Ba(Fe_{1-x}Co_x)_2As_2 from c-axis heat transport measurements
• Anisotropic Structure of the Order Parameter in FeSe0.45Te0.55 Revealed by Angle Resolved Specific Heat
• Doping evolution of the absolute value of the London penetration depth and superfluid density in single crystals of Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$
• London penetration depth in Ba(Fe${}_{1-x}$T${}_x$)${}_2$As${}_2$ (T=Co, Ni) superconductors irradiated with heavy ions
• Spin fluctuations and unconventional pairing in KFe${}_2$As${}_2$
• Effect of annealing on the specific heat of Ba(Fe1-xCox)2As2
• Magneto-optical study of Ba(Fe${}_{1-x}$T${}_x$)${}_2$As${}_2$ (T=Co, Ni) single crystals irradiated with heavy-ions
• Isotropic three-dimensional gap in the iron-arsenide superconductor LiFeAs from directional heat transport measurements
• Nodes in the Order Parameter of Superconducting Iron Pnictides Observed by Infrared Spectroscopy
• Competition between superconductivity and magnetic/nematic order as a source of anisotropic superconducting gap in underdoped Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$
• Angular-dependent upper critical field of overdoped Ba(Fe${}_{1-x}$Ni${}_x$)${}_2$As${}_2$
• Anomalous proximity effects at the interface of s and s+- superconductors
• Doping evolution of the superconducting gap structure in the underdoped iron arsenide Ba1-xKxFe2As2 revealed by thermal conductivity
• Robust s+/- pairing in CaK[Fe(1-x)Ni(x)]4As4$ (x = 0 and 0.05) from the response to electron irradiation
• Doping - dependent anisotropic superconducting gap in Na${}_{1-\delta }$(Fe${}_{1-x}$Co${}_x$)As
• ${}^{75}$As NMR of Ba(Fe${}_{0.93}$Co${}_{0.07}$)${}_2$As${}_2$ in High Magnetic Field
• Evidence for line nodes in the energy gap of the overdoped Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$ from low-temperature specific heat measurements
• Transport properties of 3D extended s-wave states in Fe-based superconductors
• Nodal superconductivity in isovalently substituted SrFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$ pnictide superconductor at the optimal doping, $x=$0.35
• Scaling of nascent nodes in extended s-wave superconductors
• Three dimensionality of band structure and a large residual quasiparticle population in Ba${}_{0.67}$K${}_{0.33}$Fe${}_2$As${}_2$ as revealed by the c-axis polarized optical measurement
• Robust accidental nodes and zeroes and critical quasiparticle scaling in iron-based multiband superconductors
• Scaling of the physical properties in Ba(Fe,Ni)2As2 single crystals: Evidence for quantum fluctuations
• Direct measurement of the temperature dependence of the magnetic penetration depth in Ba(Fe${}_{1-x}$Ni${}_x$)${}_2$As${}_2$ superconductors
• Superconducting Order Parameters in overdoped BaFe${}_{1.86}$Ni${}_{0.14}$As${}_2$ Revealed by Multiple Andreev Reflection Spectroscopy of Planar Break-Junctions
• Emergence of the minority hole with high mobility on the electrical transport in the Fe-pnictides Ba(Fe${}_{1-x}$Mn${}_x$As)${}_2$
• Linear magnetic susceptibility of anisotropic superconductors of cuboidal shape
• A Field-directional Specific Heat Study on the Gap Structure of Overdoped Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$
• Crossover of the pairing symmetry from $s$- to $d$-wave in iron pnictide superconductors
• Gap Structure of the Overdoped Iron-Pnictide Superconductor Ba(Fe${}_{0.942}$Ni${}_{0.058}$)${}_2$As${}_2$: A Low-Temperature Specific-Heat Study