Filamentary superconductivity across the phase diagram of Ba(Fe,Co) 2 As 2
H. Xiao, T. Hu, S. K. He, B. Shen, W. J. Zhang, B. Xu, K. F. He, J. Han, Y. P. Singh, H. H. Wen, X. G. Qiu, C. Panagopoulos, C. C. Almasan
Abstract
We show magnetotransport results on Ba(Fe
1−x
Co
x
)
2
As
2
(
0.0≤x≤0.13
) single crystals. We identify the low temperature resistance step at 23 K in the parent compound with the onset of filamentary superconductivity (FLSC), which is suppressed by an applied magnetic field in a similar manner to the suppression of bulk superconductivity (SC) in doped samples. FLSC is found to persist across the phase diagram until the long range antiferromagnetic order is completely suppressed. A significant suppression of FLSC occurs for
0.02<x<0.04
, the doping concentration where bulk SC emerges. Based on these results and the recent report of an electronic anisotropy maximum for 0.02
≤x≤
0.04 [Science 329, 824 (2010)], we speculate that, besides spin fluctuations, orbital fluctuations may also play an important role in the emergence of SC in iron-based superconductors.