1302.0074 (Jeehoon Kim et al.)

Intrinsic superconducting properties and vortex dynamics in heavily
overdoped Ba(Fe$_{0.86}$Co$_{0.14}$)$_2$As$_2$ single crystal    [PDF]

Jeehoon Kim, N. Haberkorn, K. Gofryk, M. J. Graf, L. Civale, F. Ronning, A. S. Sefat, R. Movshovich

In this work we report the influence of intrinsic superconducting parameters on the vortex dynamics in an overdoped Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ (x=0.14) single crystal. We find a superconducting critical temperature of 13.5 K, magnetic penetration depth $\lambda_{ab}$(0) = 660 $\pm$ 50 nm, coherence length $\xi_{ab}$(0) = 5 nm, and the upper critical field anisotropy $\gamma_{T\rightarrow Tc}$ $\approx$ 3.7. In fact, the Ginzburg-Landau model may explain the angular dependent $H_{c2}$ for this anisotropic three-dimensional superconductor. The vortex phase diagram, in comparison with the optimally doped compound, presents a narrow collective creep regime. In addition, we found no sign of correlated pinning along the c axis. Our results show that vortex core to defect size ratio and $\lambda$ play an important role in the resulting vortex dynamics in materials with similar intrinsic thermal fluctuations.

View original: http://arxiv.org/abs/1302.0074