Scanning Tunneling Spectoscopy of Iron Pnictides

本项目的目的是用高分辨率扫描隧道显微镜和能谱(STM/STS)研究低温(300mK)下砷化铁超导体的超导序参数和电子结构。在我们的研究中，我们将使用掺杂的LiVAs和NaFeAs单晶。这些材料在基态表现出一种有趣的磁性和非传统超导相的相互作用，这是铁粒子物理学的一个普遍特征。从我们的测量中，我们寻求关于电子结构和超导序参数的具体信息：i)我们将测量各种磁场中包含相敏信息的准粒子干涉，这种干涉是由准粒子对天然和掺杂杂质的散射引起的。Ii)我们将测量和比较杂质位置的态密度和清洁表面积的态密度，从中我们期望得到关于各种杂质类型的对断效应和杂质束缚态的具体信息。Iii)我们将在单个缺陷和清洁表面区域应用自旋极化扫描隧道显微镜(SP-STM)，以揭示观察到的缺陷和可能的磁有序区域的性质(磁性或非磁性)。

The aim of this project is to investigate the superconducting order parameter and the electronic structure of iron-arsenide superconductors by high-resolution scanning tunneling microscopy and spectroscopy (STM/STS) at low temperatures (down to 300 mK). For our investigations, we will use doped LiFeAs and NaFeAs single crystals. These materials exhibit an interesting interplay of magnetic and unconventional superconducting phases in the ground state, which is a generic feature of the physics of the iron pnictides. From our measurements we seek specific information about the electronic structure and the superconducting order parameter: i) We will measure the quasiparticle interference, that results from the quasiparticle scattering off natural and doped impurities and which contains phase sensitive information, in various magnetic fields. ii) We will measure and compare the densities of states at impurity sites and that of a clean surface area, from which we expect specific information about the pair-breaking effect and impurity bound-states of various impurity types. iii) We will apply spin-polarized STM (SP-STM) on individual defects and on clean surface areas in order to reveal the nature (magnetic or non-magnetic) of the observed defects and of possible magnetically ordered regions.