Theoretical study of spontaneous symmetry breaking of Fermi surface

费米面的自发对称性破缺是理论上的一个新概念。这种对称性破缺是从最近对双层铬酸盐以及铁基和铜酸盐高温超导体的实验中推断出来的。在这些实验的启发下，我们研究了与铁磁性和其他电荷顺序的竞争，由于取向对称破缺的涨落而产生的超导机制，以及可以直接检测到这种涨落的拉曼散射。利用泛函重整化群方法和标度理论进一步研究了涨落的影响，并对相变附近的一般性质提出了实验检验。用泛函重整化群研究了铁磁涨落。最后，我们实现了费米面对称破缺附近单粒子激发谱的非微扰分析。

The spontaneous symmetry breaking of the Fermi surface is a new concept found in theory. This symmetry breaking is inferred from recent experiments for bi-layered ruthenates and iron-based and cuprate high-temperature superconductors. Motivated by these experiments we studied the competition with ferromagnetism and other charge orders, a superconducting mechanism due to fluctuations of the orientational symmetry breaking, and Raman scattering which can detect such fluctuations directly. Effects of the fluctuations were explored further by employing a functional renormalization group scheme and scaling theory and we proposed an experimental test for a general property near the phase transition. Ferromagnetic fluctuations were also studied in terms of a functional renormalization group. Finally we achieved a non-perturbative analysis of the one-particle excitation spectrum near the Fermi surface symmetry breaking.