标题： SrFe$_2$As$_2$单晶中自旋密度波能隙在低温下的减弱 显示英文标题

标题： Weakening of the spin density wave gap at low temperatures in SrFe$_2$As$_2$ single crystals

摘要： 我们报告了对未掺杂的SrFe$_{2}$As$_{2}$单晶从6 K到292 K的温度依赖扫描隧道显微镜和谱学研究。电阻率数据表明在T$_{SDW}$$\approx$ 205 K处发生自旋密度波（SDW）转变，并在$\sim$ 21 K处发生超导转变，而磁化率没有显示出任何超导性。电导率图和局部隧穿谱显示在所有研究温度下表面都是电子均匀的。隧穿谱与SDW转变密切相关，在T$_{SDW}$以下费米能级附近的态密度出现下降。进一步降低温度，与SDW相关的部分能隙宽度减小。利用超导相与SDW的反相关性，我们将这个能隙减弱解释为超导性的前兆。这可能在缺陷附近促进超导性的快速成核。 显示英文摘要

摘要： We report on temperature dependent scanning tunneling microscopy and spectroscopy studies of undoped SrFe$_{2}$As$_{2}$ single crystals from 6 K to 292 K. Resistivity data show spin density wave (SDW) transition at T$_{SDW}$ $\approx$ 205 K and the superconducting transition at $\sim$ 21 K while magnetic susceptibility does not show any superconductivity. Conductance maps and local tunneling spectra show an electronically homogeneous surface at all studied temperatures. Tunnel spectra correlate well with the SDW transition with a depression in the density of states near the Fermi energy below T$_{SDW}$. On further lowering the temperature, the width of this partial energy gap associated with the SDW decreases. Using the anti-correlation of superconducting phase with SDW, we interpret this gap weakening as a precursor to superconductivity. This may give rise to a facile nucleation of superconductivity near defects.