Effect of annealing on the specific heat of Ba(Fe1-xCox)2As2

Abstract

We report on the effect of annealing on the temperature and field dependencies of the low temperature specific heat of the electron-doped Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$ for under-(x = 0.045), optimal- (x = 0.08) and over-doped (x = 0.105 and 0.14) regimes. We observed that annealing significantly improves some superconducting characteristics in Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$. It considerably increases $T_c$, decreases ${\gamma }_0$ in the superconducting state and suppresses the Schottky-like contribution at very low temperatures. The improved sample quality allows for a better identification of the superconducting gap structure of these materials. We examine the effects of doping and annealing within a self-consistent framework for an extended s-wave pairing scenario. At optimal doping our data indicates the sample is fully gapped, while for both under and overdoped samples significant low-energy excitations possibly consistent with a nodal structure remain. The difference of sample quality offers a natural explanation for the variation in low temperature power laws observed by many techniques.

9 pages: added references, two figures and supplementary information; Accepted to Physical Review B (Jan 10, 2010)

References in corpus (19)

• Superconductivity at 38 K in the iron arsenide (Ba1-xKx)Fe2As2
• Superconductivity at 43 K in Samarium-arsenide Oxides $SmFeAs{O}_{1-x}{F}_x$
• Superconductivity at 22 K in Co-doped BaFe2As2 Crystals
• 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
• Pairing Symmetry in a Two-Orbital Exchange Coupling Model of Oxypnictides
• Multiband magnetism and superconductivity in Fe-based compounds
• Scanning Tunneling Spectroscopy and Vortex Imaging in the Iron-Pnictide Superconductor BaFe${}_{1.8}$Co${}_{0.2}$As${}_2$
• Spin susceptibility, phase diagram, and quantum criticality in the electron-doped high Tc Superconductor Ba[Fe(1-x)Co(x)]2As2
• 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
• 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
• Momentum dependence and nodes of the superconducting gap in iron-pnictides
• Origin of Gap Anisotropy in Spin Fluctuation Models of the Fe-pnictides
• Lifting of nodes by disorder in extended-$s$ state superconductors: application to ferropnictides
• Specific heat evidence for two-gap superconductivity in ternary-iron silicide Lu${}_2$Fe${}_3$Si${}_5$
• Nanoscale superconducting gap variations, strong coupling signatures and lack of phase separation in optimally doped BaFe1.86Co0.14As2
• A doping dependent specific heat study of the superconducting gap in Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$
• Heat capacity study of BaFe${}_2$As${}_2$: effects of annealing
• Superfluid Density and Field-Induced Magnetism in Ba(Fe1-xCox)2As2 and Sr(Fe1-xCox)2As2 Measured with Muon Spin Relaxation

Cited by in corpus (2)

• Calorimetric Evidence of Strong-Coupling Multiband Superconductivity in Fe(Te0.57Se0.43) Single Crystal
• ${}^{75}$As NMR of Ba(Fe${}_{0.93}$Co${}_{0.07}$)${}_2$As${}_2$ in High Magnetic Field