Fe位Ru等电子取代对最佳F掺杂SmFeAsO能隙的影响
Effects of isoelectronic Ru substitution at the Fe site on the energy gaps of optimally F-doped SmFeAsO
摘要：
利用点接触Andreev反射光谱研究了Fe位等电子Ru取代对最佳F掺杂SmFeAsO能隙的影响。结果表明，SmFe_{1-x} Ru_{x} AsO_{0.85} F_{0.15}体系至少在x=0.50时保持多能隙特征，能隙振幅Δ 1和Δ 2与局域临界温度TcA几乎成线性关系.间隙比2 Δ_1/（kB Tc）仅在Tc > 30 K时保持近似恒定，但当Tc进一步降低时急剧增加。这种趋势似乎是共同的许多铁基超导体，无论他们的家庭。基于能带结构和投影在不同能带上的态密度的第一原理计算，我们表明，这种趋势，以及间隙的Tc依赖性和Ru掺杂后Tc的降低，可以在有效的三带Eliashberg模型内解释为由于在有限温度下超流密度的抑制，反过来，改变了特征自旋涨落能量的温度依赖性。
英文摘要：
We studied the effects of isoelectronic Ru substitution at the Fe site on the energy gaps of optimally F-doped SmFeAsO by means of point-contact Andreev reflection spectroscopy. The results show that the SmFe_{1-x}Ru_{x}AsO_{0.85}F_{0.15} system keeps a multigap character at least up to x=0.50, and that the gap amplitudes Delta_1 and Delta_2 scale almost linearly with the local critical temperature TcA. The gap ratios 2Delta_i/(kB Tc) remain approximately constant only as long as Tc > 30 K, but increase dramatically when Tc decreases further. This trend seems to be common to many Fe-based superconductors, irrespective of their family. Based on first-principle calculations of the bandstructure and of the density of states projected on the different bands, we show that this trend, as well as the Tc dependence of the gaps and the reduction of Tc upon Ru doping, can be explained within an effective three-band Eliashberg model as being due to a suppression of the superfluid density at finite temperature that, in turns, modifies the temperature dependence of the characteristic spin-fluctuation energy.
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