Non-exponential London penetration depth in Ba${}_{1-}$K${}_x$Fe${}_2$As${}_2$ single crystals

Abstract

We have studied the in- and out-of-plane magnetic penetration depths in the hole- doped iron based superconductor Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$ ($T_c\approx$ 30K). The study was performed on single crystals grown from different fluxes and we find that the results are nearly the same. The in-plane London penetration depth ${\lambda }_{ab}$ does not show exponential saturation at low temperature, as would be expected from a fully gapped superconductor. Instead, ${\lambda }_{ab}(T)$ shows a power-law behavior, $\lambda \propto T^n$ ($n\approx 2$), down to $T\approx 0.02T_c$, similar to the electron doped Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$. The penetration depth anisotropy ${\gamma }_{\lambda }={\lambda }_c(T)/{\lambda }_{ab}(T)$ increases upon cooling, opposite to the trend observed in the anisotropy of the upper critical field, ${\gamma }_{\xi }=H_{c2}^{\perp c}(0)/H_{c2}^{\parallel c}(0)$. These are universal characteristics of both the electron and hole doped 122 systems, suggesting unconventional superconductivity. The behavior of the in-plane superfluid density ${\rho }_{ab}(T)$ is discussed in light of existing theoretical models proposed for the iron pnictides superconductors.

References in corpus (24)

• Spin density wave anomaly at 140 K in the ternary iron arsenide BaFe2As2
• Observation of Fermi-surface-dependent nodeless superconducting gaps in Ba0.6K0.4Fe2As2
• 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
• Anisotropic thermodynamic and transport properties of single crystalline (Ba${}_{1-x}$K${}_x$)Fe${}_2$As${}_2$ (x = 0 and 0.45)
• Magnetic Penetration Depth in Unconventional Superconductors
• Superconductivity and Crystal Structures of (Ba1-xKx)Fe2As2 (x = 0 - 1)
• Multiband magnetism and superconductivity in Fe-based compounds
• Evidence for nodal superconductivity in LaFePO
• Superconducting gap symmetry of Ba0.6K0.4Fe2As2 studied by angle-resolved photoemission spectroscopy
• Multiple Nodeless Superconducting Gaps in (Ba0.6K0.4)Fe2As2 Superconductor from Angle-Resolved Photoemission Spectroscopy
• Determination of anisotropic Hc2 up to 60 T in (Ba0.55K0.45)Fe2As2 single crystals
• Probing superconducting energy gap from infrared spectroscopy on a Ba${}_{0.6}$K${}_{0.4}$Fe${}_2$As${}_2$ single crystal with T${}_c$=37 K
• Anisotropy of the Optimally-Doped Iron Pnictide Superconductor Ba(Fe0.926Co0.074)2As2
• Microwave Surface-Impedance Measurements of the Magnetic Penetration Depth in Single Crystal Ba1-xKxFe2As2 Superconductors: Evidence for a Disorder-Dependent Superfluid Density
• 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
• Growth and characterization of A_{1-x}K_xFe_2As_2 (A = Ba, Sr) single crystals with x=0 - 0.4
• Superfluid density and penetration depth in Fe-pnictides
• Experimental Consequences of the S-wave $\cos (k_x)\cdot \cos (k_y)$ Superconductivity in the Iron-Pnictides
• The London penetration depth in single crystals of Ba(Fe_{1-x}Co_x)_2As_2 at various doping levels
• Evidence for two-gap superconductivity in (Ba,K)Fe_2As_2 by directional point contact Andreev reflection spectroscopy
• 75As NMR Study of Hole-Doped Superconductor Ba1-xKxFe2As2 (Tc = 38K)
• Evidence for Charge Glass-like Behavior in Lightly Doped La_{2-x}Sr_{x}CuO_{4} at Low Temperatures

Cited by in corpus (14)

• Momentum dependence and nodes of the superconducting gap in iron-pnictides
• Temperature dependence of lower critical field Hc1(T) shows nodeless superconductivity in FeSe
• Quasiparticle Heat Transport in Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$: Evidence for a k-dependent Superconducting Gap without Nodes
• Local measurement of the superfluid density in the pnictide superconductor Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$ across the superconducting dome
• Optical properties of the iron-arsenic superconductor BaFe1.85Co0.15As2
• Effects of electron irradiation on resistivity and London penetration depth of Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$ ($x\le$ 0.34) iron - pnictide superconductor
• Competition between superconductivity and magnetic/nematic order as a source of anisotropic superconducting gap in underdoped Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$
• Leggett mode in a strong-coupling model of iron arsenide superconductors
• Signature of multigap nodeless superconductivity in fluorine-doped NdFeAsO
• Magnetic penetration-depth measurements of a suppressed superfluid density of superconducting Ca${}_{0.5}$Na${}_{0.5}$Fe${}_2$As${}_2$ single crystals by proton irradiation
• Infrared probe of the gap evolution across the phase diagram of Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$
• SANS Study of Vortex Lattice Structural Transition in Optimally Doped (Ba${}_{1-x}$K${}_x$)Fe${}_2$As${}_2$
• Direct measurement of the temperature dependence of the magnetic penetration depth in Ba(Fe${}_{1-x}$Ni${}_x$)${}_2$As${}_2$ superconductors
• Large increase of the anisotropy factor in the overdoped region of Ba(Fe${}_{1-x}$Ni${}_x$)${}_2$As${}_2$ as probed by fluctuation spectroscopy