We report on the effect of annealing on the temperature and field dependencies of the low-temperature specific heat of the electron-doped Ba(Fe1-xCox)2As2 for under- (x = 0.045), optimally (x = 0.08), and over- (x = 0.105 and 0.14) doped regimes. We observed that annealing significantly improves some superconducting characteristics in Ba(Fe1-xCox)2As2. It considerably increases Tc, decreases γ0 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 indicate that the sample is fully gapped, while for both under- and overdoped samples significant low-energy excitations remain, possibly consistent with a nodal structure. The difference of sample quality offers a natural explanation for the variation in low-temperature power laws observed by many techniques. © 2011 American Physical Society.
Publication Source (Journal or Book title)
Physical Review B - Condensed Matter and Materials Physics
Gofryk, K., Vorontsov, A., Vekhter, I., Sefat, A., Imai, T., Bauer, E., Thompson, J., & Ronning, F. (2011). Effect of annealing on the specific heat of Ba(Fe1-xCo x)2As2. Physical Review B - Condensed Matter and Materials Physics, 83 (6) https://doi.org/10.1103/PhysRevB.83.064513