Unconventional London penetration depth in Ba(Fe0.93Co0.07)2As2 single crystals

Abstract

The London penetration depth, $\lambda (T)$, has been measured in several single crystals of Ba(Fe${}_{0.93}$Co${}_{0.07}$)${}_2$As${}_2$. Thermodynamic, electromagnetic, and structural characterization measurements confirm that these crystals are of excellent quality. The observed low temperature variation of $\lambda (T)$ follows a power-law, $\Delta \lambda (T)\sim T^n$ with $n=2.4\pm 0.1$, indicating the existence of normal quasiparticles down to at least $0.02T_c$. This is in contrast to recent penetration depth measurements on single crystals of NdFeAsO${}_{1-x}$F${}_x$ and SmFeAsO${}_{1-x}$F${}_x$, which indicate an anisotropic but nodeless gap. We propose that a more three-dimensional character in the electronic structure of Ba(Fe${}_{0.93}$Co${}_{0.07}$)${}_2$As${}_2$ may lead to an anisotropic $s-$wave gap with point nodes that would explain the observed $\lambda (T)$.

4 pages

References in corpus (10)

• Superconductivity at 38 K in the iron arsenide (Ba1-xKx)Fe2As2
• Magnetism, superconductivity, and pairing symmetry in Fe-based superconductors
• Small anisotropy, weak thermal fluctuations, and high field superconductivity in Co-doped iron pnictide Ba(Fe1-xCox)2As2
• The BCS-like gap in superconductor SmFeAsO_0.85F_0.15
• Vortex phase diagram of Ba(Fe0.93Co0.07)2As2 single crystals
• Microwave Penetration Depth and Quasiparticle Conductivity in PrFeAsO_1-y Single Crystals : Evidence for a Full-Gap Superconductor
• Momentum dependence of the superconducting gap in Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$
• Anisotropy of the Optimally-Doped Iron Pnictide Superconductor Ba(Fe0.926Co0.074)2As2
• NMR relaxation rate in superconducting pnictides: extended $s_{\pm }$ scenario
• Possible two-gap superconductivity in NdFeAs(O,F) probed by point-contact Andreev-reflection spectroscopy

Cited by in corpus (9)

• Microwave Surface-Impedance Measurements of the Magnetic Penetration Depth in Single Crystal Ba1-xKxFe2As2 Superconductors: Evidence for a Disorder-Dependent Superfluid Density
• Momentum dependence and nodes of the superconducting gap in iron-pnictides
• Momentum-resolved superconducting gap in the bulk of Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$ from combined ARPES and $\mu$SR measurements
• Superfluid density and penetration depth in Fe-pnictides
• Quasiparticle Heat Transport in Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$: Evidence for a k-dependent Superconducting Gap without Nodes
• Non-exponential London penetration depth in Ba${}_{1-}$K${}_x$Fe${}_2$As${}_2$ single crystals
• Theory of Raman response in a superconductor with extended s-wave symmetry: Application to Fe-pnictides
• Superconductivity without Fe or Ni in the phosphides BaIr2P2 and BaRh2P2
• Penetration depth, lower critical fields, and quasiparticle conductivity in Fe-arsenide superconductors