镧系大磁阻材料在压力下的电子结构演化和超导电性的理论研究

磁阻效应和超导电性一直是物理学家关注的重要物理问题。最近，实验上发现一些非磁性材料在常压下展示出巨大的正磁阻效应，达到百分之1万至1300万，随着外界压力的增加，磁阻效应逐渐被压制而超导电性出现。关于这些新奇现象的物理机制，目前国际上还存在着争论。. 在我们以往工作的基础上，本项目将以镧系大磁阻材料为模板，通过数值计算和模型分析，研究材料的大磁阻效应和压力下超导电性的起源。我们将研究材料的结构和电子结构在不同压力下的演化，考察材料中载流子的浓度、比例以及材料的拓扑性质随压强的变化关系，检查大磁阻效应的电荷补偿、拓扑保护等机制，并研究大磁阻效应在压力下被抑制的原因，通过计算材料的电声耦合，探索材料在压力下的超导起源，探讨超导与大磁阻态之间的关联，从而为更好地理解相关物理机制以及寻找更多的新型功能材料提供参考。

The mechanisms of magnetoresistance and superconductivity have long been the concern of condensed matter physicists. Recently, it has been found that several nonmagnetic semimetal materials, which demonstrate extreme magnetoresistance (XMR) up to 10^7 percent at ambient pressure, show suppressed magnetoresistance but emerging superconductivity under high pressure. For the underlying physical mechanisms of these exotic phenomena, a consensus has not yet been achieved..Based on our previous studies, we will use the lanthanide-based XMR materials as model systems to theoretically study the origins of the XMR effect and the superconductivity with suppressed MR under pressure. We will investigate the pressure-dependent structures and electronic structures of these materials, and will calculate their corresponding carrier densities/ratios and topological properties. For the XMR effect, we will check the charge compensation mechanism, the topological protection mechanism, etc., and will find out the reason for the suppressed MR under pressure. By studying the electron-phonon coupling, we will explore the origination of the induced superconductivity as well as the correlation between the superconductivity and the XMR state. Combined with on-going experimental findings, our studies may provide implications on understanding the related physical mechanisms and on exploring new functional materials.