Tuesday, July 9, 2013

1307.1908 (H. Z. Arham et al.)

Andreev Reflection Like Enhancement Above Bulk $T_c$ in Electron
Underdoped Iron Arsenides

H. Z. Arham, C. R. Hunt, J. Gillett, S. D. Das, S. E. Sebastian, D. Y. Chung, M. G. Kanatzidis, L. H. Greene
We use point contact spectroscopy (PCS) to probe the superconducting properties of electron doped $\rm{Ba(Fe_{1-x}Co_x)_2As_2}$ ($\rm{x = 0.05, 0.055, 0.07, 0.08}$) and hole doped $\rm{Ba_{0.8}K_{0.2}Fe_2As_2}$. PCS directly probes the low energy density of states via Andreev reflection, revealing two distinct superconducting gaps in both compound families. Apart from the electron underdoped $\rm{Ba(Fe_{1-x}Co_{x})_2As_2}$, the excess current due to Andreev reflection for the compounds follows the typical BCS temperature dependence. For underdoped $\rm{Ba(Fe_{1-x}Co_{x})_2As_2}$, the temperature dependence of the excess current deviates from that of BCS, developing a tail at higher temperatures and surviving above bulk $T_c$. Possible explanations for this anomalous behavior are explored.
View original: http://arxiv.org/abs/1307.1908

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