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

2013/07/07 by Hamood Z. Arham, C. R. Hunt, Arham, H. Z. +13
Materials Science · Physics and Astronomy · #Iron-based superconductors research #Rare-earth and actinide compounds #Physics of Superconductivity and Magnetism

paper · pdf · doi:10.48550/arxiv.1307.1908

Abstract

We use point contact spectroscopy (PCS) to probe the superconducting properties of electron doped \rmBa(Fe_1-xCo_x)₂As₂ (\rmx = 0.05, 0.055, 0.07, 0.08) and hole doped \rmBa_0.8K_0.2Fe₂As₂. 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 \rmBa(Fe_1-xCo_x)₂As₂, the excess current due to Andreev reflection for the compounds follows the typical BCS temperature dependence. For underdoped \rmBa(Fe_1-xCo_x)₂As₂, 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.

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