Many-body effects in the electronic structure and the superconductivity of adsorbates on semiconductor surfaces

本项目继续并扩展了我们对半导体表面上电子结构和吸附物新兴相中的多体效应的研究。覆盖/掺杂的变化允许在与几何挫折（三角形晶格）竞争的传统能带理论之外的电子相关性的受控研究。在第一部分，我们在方法论（LDA +变分聚类方法、LDA + DMFT、QMC、功能重整化群）的基础上，重点研究了Mott跃迁，并预测了特定双原子体系中潜在的几何和新出现的磁序。在P1项目的密切合作下，该磁序的指纹在光谱中被识别出来，例如相应的光电光谱。在后续研究中，我们希望(i)解决可能的自旋液相，（ii）系统地将我们的研究扩展到超导性，例如最近在Si（111）上检测到的Pb（In）的超导性。在这里，普遍感兴趣的问题是可能的二维超导状态的脆弱性质，容易受到强量子相波动和库珀配对的胶水的影响。此外，我们专注于（iii）自旋轨道耦合的作用和（iv）非常规拓扑超导（SC）的新途径。第（iii）部分的动机来自于我们对Au/Ge系统的强自旋轨道耦合的发现（与P1），其中发现了与拓扑绝缘体Bi2Te3的表面狄拉克态惊人的相似性。在第（iv）部分中，我们重点研究了具有复杂配对间隙和时间反转对称性破缺的手性SC。这种非平凡拓扑具有异常丰富的现象，如量子自旋和热霍尔电导以及边缘电流，这些现象与复杂的配对间隙一起可以在实验中搜索。最后，我们想要研究强自旋轨道耦合和SC的结合，并研究在合原子系统中是否可以实现配对（单重态+三重态）混合的激发可能性。

This project continues and extends our study of many-body effects in the electronic structure and emerging phases of adsorbates on semiconductor surfaces. The variation of coverage/ doping allows for a controlled study of electronic correlations beyond traditional band theory in competition with geometrical frustration (triangular lattice). In the first period, on the basis of progress in methodology (LDA + Variational Cluster Approaches, LDA + DMFT, QMC, Functional Renormalization Group), we concentrated on the Mott transition and predicted the underlying geometrical and emerging magnetic orders in specific adatomic systems. In close collaboration with project P1, the fingerprints of this magnetic order were identified in spectroscopies, such as the corresponding photoemission spectra. In the continuation, we would like to (i) address possible spin-liquid phases and (ii) systematically extend our studies to superconductivity such as the recently detected superconductivity in the Pb(In) on Si(111). Here, questions of general interest are the fragile nature of a possible 2D superconducting state, susceptible to strong quantum-phase fluctuations and the glue for Cooper-pairing. Furthermore, we concentrate on (iii) the role of spin-orbit coupling and (iv) new paths to unconventional topological superconductivity (SC). Part (iii) is motivated from our findings (with P1) for the Au/Ge system with its strong-spin orbit coupling, where a striking similarity was detected to the surface Dirac state of the topological insulator Bi2Te3. In Part (iv), we focus on chiral SC with a complex pairing gap and time-reversal symmetry breaking. This non-trivial topology has an exceptionally rich phenomenology such as a quantum-spin and thermal Hall conductance as well as edge currents, which, together with the complex pairing gap, can be searched for in experiments. Last but not least, we want to study the combination of strong spin-orbit coupling and SC, and investigate whether the exciting possibility of pairing (singlet + triplet) mixing can be realized in adatom systems.