铜氧化物高温超导体的本质被认为是其独特地在准二维正方格子上实现了一个具有较强交换耦合的单带自旋-1/2 Heisenberg反铁磁体。由于强自旋-轨道耦合的作用，铱氧化物Sr2IrO4是铜氧化物外第一个也能实现该情况的材料，这自然导致人们期望它能成为实现高温超导的另一个平台。虽然Sr2IrO4在掺杂后呈现出费米口袋、费米弧和d波能隙等跟掺杂铜氧化物惊人相似的电子结构，但实验还没有观测到超导的证据。理解这些奇异电子态的本质是讨论Sr2IrO4能否超导的基础。本项目将结合唯象理论分析和微观模型计算，研究Sr2IrO4中电子关联、自旋-轨道耦合的影响及它们之间的相互作用，探讨赝能隙和d波能隙的本质以及它们和反铁磁态三者之间的关系。我们将讨论Sr2IrO4中的电子掺杂和它导致电子态不均匀性的机制。这些电子态与铜氧化物中对应电子态之间的对比可能会为我们理解非常规高温超导电性提供的新线索。

The essence of the cuprate high-Tc superconductor is believed to be contained in its unique realization of a single-band spin-1/2 Heisenberg antiferromagnet on a quasi-two-dimensional square lattice, with strong spin exchange coupling. Owing to its strong spin-orbit coupling, iridate Sr2IrO4 is the first material outside of the cuprate family that also realizes this condition. This naturally leads to the expectation that Sr2IrO4 can be another platform for unconventional high-Tc superconductivity. Despite the fact that the low-energy electronic structure of the carrier-doped Sr2IrO4 share some remarkable similarities with the cuprates, including Fermi surface pockets, Fermi arcs, and d-wave gap, there is not yet firm evidence for superconductivity in Sr2IrO4. Whether a superconducting state exists in Sr2IrO4 requires understanding the nature of these observed novel correlated spin-orbit entangled electronic states. By using phenomenological theory analysis and microscopic model calculation, we plan to investigate, in this project, the effects of electron correlations, spin-orbit coupling and their interplay in Sr2IrO4; the nature of the pseudogap, d-wave gap, and their relationship with antiferromagnetism. The mechanism of electron doping and the induced electronic inhomogeneity will also be discussed. The similarities and differences between these emergent novel electronic states and their counterparts in cuprates may shed new light on our understanding of the unconventional high-Tc superconductivity.