Interplay between symmetry breaking distortions and superconductivity in layered oxides

层状氧化物中对称破缺畸变与超导性之间的相互作用

• 批准号: 2126478
• 金额: --
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2126478
• 关键词: Interplay; between; symmetry; breaking; distortions

The discovery of high-temperature superconductivity (HTS) in the La2-xBaxCuO4 Ruddlesden-Popper (RP) system in 1986 has stimulated a tremendous amount of research in understanding the origin of this unconventional superconductivity. The underlying mechanisms leading to such phenomena in the cuprates cannot be explained by BardeenCooper-Schrieffer (BCS) theory, which argues that conventional superconductivity arises due to small attractive interactions between electrons, causing them to form Cooper pairs and condense. Despite intensive research efforts in understanding the wealth of unusual properties these cuprates exhibit, there currently exists no microscopic theory which can account for all of their properties. It has been proposed that superconductivity arises due to electron-phonon coupling mediated by Jahn-Teller polarons, but the exact nature of these quasiparticles and their coupling to the lattice remains elusive. Superconductivity in the RP cuprates only seems to arise in a single space group of orthorhombic symmetry and vanishes upon a structural phase transition to a tetragonal phase at low temperatures. In this project, we use theory and simulation based on firstprinciples calculations to investigate the phase transition from orthorhombic to tetragonal at low temperatures. This should help gain better insight into the nature of the lattice coupling giving rise to superconductivity in the orthorhombic system.

1986年La_（2-x）CuO_4-Ruddlesden-Popper（RP）体系高温超导性的发现，激发了人们对这种非常规超导性起源的大量研究。BardeenCooper-Schrieffer（BCS）理论无法解释铜氧化物中导致这种现象的潜在机制，该理论认为，传统的超导性是由于电子之间的小吸引力相互作用，导致它们形成库珀对并凝聚而产生的。尽管深入的研究努力，以了解这些铜酸盐展示的不寻常的属性的财富，目前还没有微观理论可以解释它们的所有属性。有人提出，超导性是由于Jahn-Teller极化子介导的电子-声子耦合而产生的，但这些准粒子的确切性质及其与晶格的耦合仍然难以捉摸。超导电性的RP铜酸盐似乎只出现在一个单一的空间群的正交对称性和消失后，在低温下的结构相变到一个tetraxylase相。在这个项目中，我们使用基于第一性原理计算的理论和模拟来研究在低温下从正交晶系到四方晶系的相变。这应该有助于更好地了解斜方晶系中产生超导性的晶格耦合的本质。