Emergent multicomponent phases and odd parity in unconventional superconductors

我们的联合理论和实验方案的总体目标是更好地理解在多轨道存在、强自旋轨道耦合与潜在的非平凡的能带结构拓扑以及电子-电子和配对关联的微妙相互作用的情况下，非传统超导体中新出现的多组分相的形成。这些例子既有中等关联的系统，如具有奇宇称向列超导电性的铜、Nb或锶插层Bi2Se_3，也有强关联的系统，如铁基超导体和Sr2RuO4。这一提议的主要目的之一是从理论和实验上探索这些态的配对涨落的热力学和光谱特征及其与磁、轨道和向列相不稳定性的竞争，并揭示它们的微观起源和对超导电性的反馈。我们计划研究Bi2Se_3和相关(近邻诱导的)体系中电子关联适中的奇宇称向列相超导电性的形成，探索范德华力在库珀配对形成中的作用。另一方面，我们计划研究铁基硫系超导体和Sr2RuO4，在这些超导体中，强电子关联和强自旋轨道耦合同时发生。显然，强大的电子关联使他们的理论和实验研究在技术上更具挑战性。在这里，我们计划进一步发展相敏技术来确定多轨道情况下超导带隙的相结构，并研究非平凡能带拓扑的潜在作用。这项工作的具体目标是对现有的新颖实验进行真实的微观描述，在定量水平上描述这些系统的热力学和光谱(STM)特征。

The overall goal of our joint theoretical and experimental proposal is to better understand the formation of emergent multicomponent phases in unconventional superconductors in the presence of multiple orbitals, strong spin-orbit coupling with potentially non-trivial topology of the band structure, and the delicate interplay of electron-electron and pairing correlations. The examples range from moderately correlated systems such as Cu, Nb, or Sr intercalated Bi2Se3 with odd parity nematic superconductivity to strongly-correlated systems such as iron-based superconductors and Sr2RuO4. One of the main objectives of this proposal is to explore theoretically and experimentally the thermodynamic and spectroscopic features of the pairing fluctuations of these states and their competition with magnetic, orbital, and nematic instabilities and to reveal their microscopic origin and feedback on superconductivity. We plan to study the formation of the odd-parity nematic superconductivity in Bi2Se3 and related (proximity-induced) systems where electronic correlations are moderate exploring the role of van der Waals forces in the formation of the Cooper-pairing. On the other hand we plan to investigate the Fe-based chalcogenide superconductors and Sr2RuO4, where strong electronic correlations occur together with strong spin-orbit coupling. Clearly strong electronic correlations make their theoretical and experimental investigation technically more challenging. Here, we plan to further develop the phase sensitive technique to determine the phase structure of the superconducting gap in multiorbital case and study the potential role of non-trivial band topology. The specific objective of the endeavor is to develop a genuine microscopic description of the available novel experiments that describes thermodynamic and spectroscopic (STM) features of these systems on a quantitative level.