Nematic phase of Iron Based Superconductors probed by Nernst effect

用能斯特效应探测铁基超导体的向列相

• 批准号: 392673109
• 负责人: Dr. Federico Caglieris, Ph.D.
• 金额: --
• 依托单位: Institut für Festkörperforschung
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/392673109?language=en
• 关键词: Nematic; phase; Iron; Based; Superconductors

An important and very controversial topic in modern condensed matter physics is the understanding of the so-called nematic order, which consists of a self-organized electronic state that breaks the rotational symmetry of the underlying lattice but keeps the translational symmetry. The nematic order is considered to play an important role in many strongly correlated materials and it is a well established fact in two dimensional electron systems, strontium ruthenates, superconducting cuprates and iron based superconductors (IBS). In particular, in the last years, the nematic fluctuations in IBS, have been object of intense investigation since they are claimed to be crucial for the Cooper pairing mechanism in unconventional superconductors. Thanks to the richness of their phase diagram, IBS are the ideal environment to investigate the relationship between the electronic nematicity and the rising of long-range magnetic orders, superconductivity and quantum criticality. Among the possible techniques to investigate the nematic phenomenology, thermoelectric transport properties, namely Seebeck and Nernst effect, have been pointed out as an extremely powerful probe, but their systematic application is still missing. With this project I want to fill this gap. In particular, I want to adopt a novel and original approach by using uniaxial strain/stress as a tunable parameter in the Nernst effect measurements. In fact, in recent experiments, the application of uniaxial pressure to induce structural distortions, revealed to be a fundamental ingredient to investigate the nematic phase/fluctuations. In particular very interesting and promising results have been obtained through electric resistivity measurements as a function of uniaxial strain. Indeed, thermoelectric properties are predicted to be far more sensitive, opening completely new insights into this novel aspect of the physics of correlated electron systems.My method is sophisticated since it requires the integration of a device for the application of uniaxial strain, like a piezoelectric, in a state-of-the-art thermoelectric measurement setup. However, I do not only expect important results in the field of nematic fluctuations of IBS but I will also establish a technique promising for much more physical questions. For example, the Nernst effect is known to be a sensitive probe of superconducting fluctuations whose strain derivatives can be studied with the new device. Moreover, topological states strongly affect magnetotransport and the Nernst effect. Therefore the device developed within this project can, in long-term, also be used to investigate topological states, for example by tuning the position of Weyl points.

在现代凝聚态物理学中，对所谓向列序的理解是一个重要而又非常有争议的话题。向列序由一个自组织的电子态组成，它打破了底层晶格的旋转对称性，但保持了平动对称性。向列序被认为在许多强相关材料中起着重要作用，在二维电子系统、钌酸锶、超导铜酸盐和铁基超导体（IBS）中都是一个公认的事实。特别是，在过去的几年里，IBS的向列波动一直是深入研究的对象，因为它们被认为对非常规超导体中的库珀配对机制至关重要。由于其相图的丰富性，IBS是研究电子向列性与长程磁序上升、超导性和量子临界性之间关系的理想环境。在研究向列现象学的可能技术中，热电输运性质，即塞贝克和能斯特效应，已经被指出是一个非常强大的探针，但它们的系统应用仍然缺失。通过这个项目，我想填补这一空白。特别是，我想采用一种新颖和原创的方法，即在能斯特效应测量中使用单轴应变/应力作为可调参数。事实上，在最近的实验中，应用单轴压力诱导结构畸变，是研究向列相/波动的基本因素。特别是通过测量电阻率作为单轴应变的函数得到了非常有趣和有希望的结果。事实上，热电性质被预测要敏感得多，为相关电子系统物理学的这个新方面开辟了全新的见解。我的方法很复杂，因为它需要在最先进的热电测量装置中集成用于单轴应变应用的设备，如压电。然而，我不仅期望在肠易激综合征的向列波动领域取得重要成果，而且还将建立一种有希望解决更多物理问题的技术。例如，已知能斯特效应是超导波动的敏感探针，其应变导数可以用新装置研究。此外，拓扑态强烈影响磁输运和能思特效应。因此，在这个项目中开发的设备，从长远来看，也可以用于研究拓扑状态，例如通过调整Weyl点的位置。