Tunneling spectroscopy and transport properties of FeSe thin films

这个项目的目的是为了更好地了解铁镍化合物/-合晶化合物和相关化合物的超导机理。我们研究了化合物FeSe(和掺杂的FeSe1-xTex)，这是这类材料结构最简单的代表。外延薄膜被用作具有确定的几何形状和良好有序表面的样品，这对于预期的研究是必要的或有利的。研究薄膜厚度和超导转变温度与衬底的依赖关系，重点研究衬底-薄膜相互作用产生的晶格扭曲(外延应力)将有助于更好地理解样品性质与制备条件的显著相关性。我们的目标是通过平面结上的隧道光谱直接研究超导能隙和超导的机制(强耦合特性)。此外，通过在具有晶界的衬底上沉积薄膜，可以实现用于研究有序参数对称性的平面内约瑟夫森结。对上临界场进行与角度相关的补充测量，可以获得超导序参数的对称性。对FeSe_(1-x)Tex薄膜的霍尔效应和热功率测量提供了有关掺杂水平相关的费米面的信息。

The aim of this project is to gain an improved understanding of the mechanism of superconductivity of ironpnictides/ -chalocogenides and related compounds. We investigate the compound FeSe (and doped FeSe1-xTex), the structurally simplest representative of this class of materials. Epitaxial thin films are used as samples with a defined geometry and well-ordered surface, as necessary or advantageous for the intended investigations.A study of the films thickness and substrate dependence of the superconducting transition temperature focusing on lattice distortions generated by the substrate – thin film interaction (epitaxial stress) will help to improve the understanding of the pronounced preparation condition dependence of the sample properties.We aim at the direct investigation of the superconducting energy gap and the mechanism of superconductivity (strong coupling features) by tunneling spectroscopy on planar junctions. Additionally, by film deposition on substrates with grain boundaries in-plane Josephson junctions for the investigation of the order parameter symmetry can be realised. Supplementary, angular dependent measurements of the upper critical field can provide access to the symmetry of the superconducting order parameter. Hall-effect and Thermopower measurements on FeSe1-xTex thin films give information concerning the doping level dependent Fermi-surfaces.