论文标题
在沮丧的费米子梯子中，光谱，Lifshitz的过渡和轨道电流均匀
Spectrum, Lifshitz transitions and orbital currents in frustrated fermionic ladders with a uniform flux
论文作者
论文摘要
具有合成量规场的Ultrocold费米气体代表了研究晶格挫败感和有效磁通量的综合效果的绝佳平台，并且有效的磁通量接近每个粒子的一个通量量子。完成此任务的最小理论模型是在三角形的两链通量阶梯上的无旋转非互动费米的系统。在本文中，我们考虑了这种模型接近一半的模型，沿梯子的锯齿形键交替进行链跳跃振幅，并且很小。在模型的基态特性的定性变化中，最值得注意的是，磁通量诱导的拓扑LIFSHITTINIONS转变朝着接近Flux量子（$ f \ f \ sim 1/2 $）的每个diotomic Plaquette（$ f $）的通量值转移。晶格的几何挫败感会破坏非填充梯子中存在的$ k \ to-k $粒子孔光谱对称性，并导致金属 - 绝缘体过渡时的退化分裂。翻译不变的三角形梯子的一个了不起的特征是在布里鲁因区域边界上出现孤立的迪拉克节点，使地面状态在$ f = 1/2 $ semi-setallic中。我们计算轨道电流的通量依赖性，并通过这种依赖性在恒定的化学势$μ$和恒定粒子密度$ρ$的依赖性中识别LifShitz的临界点。三角形梯子中没有粒子孔对称性的不存在导致粒子（$ρ> 1 $）和孔（$ρ<1 $）之间的不对称性兴奋剂（$ρ<1 $），并且在阶段图，lifshitz点，lifshitz点和轨道依赖性的质量不同的结果上，在设置$ρ= = = {$ rm const $ const $和$ rm const} $ cont} $ cont} $ cont} $ cont} $ cont} $ and和$ cont} $ and和$。
Ultracold Fermi gases with synthetic gauge field represent an excellent platform to study the combined effect of lattice frustration and an effective magnetic flux close to one flux quantum per particle. The minimal theoretical model to accomplish this task is a system of spinless noninteracting fermions on a triangular two-chain flux ladder. In this paper we consider this model close to half-filling, with interchain hopping amplitudes alternating along the zigzag bonds of the ladder and being small. In such setting qualitative changes in the ground state properties of the model, most notably the flux-induced topological Lifshitz transitions are shifted towards the values of the flux per a diatomic plaquette ($f$) close to the flux quantum ($f\sim 1/2$). Geometrical frustration of the lattice breaks the $k \to π- k$ particle-hole spectral symmetry present in non-frustrated ladders, and leads to splitting of the degeneracies at metal-insulator transitions. A remarkable feature of a translationally invariant triangular ladder is the appearance of isolated Dirac node at the Brillouin zone boundary, rendering the ground state at $f=1/2$ semi-metallic. We calculate the flux dependence of the orbital current and identify Lifshitz critical points by the singularities in this dependence at a constant chemical potential $μ$ and constant particle density $ρ$. The absence of the particle-hole symmetry in the triangular ladder leads to the asymmetry between particle ($ρ>1$) and hole ($ρ<1$) doping and to qualitatively different results for the phase diagram, Lifshitz points and the flux dependence of the orbital current in the settings $ρ={\rm const}$ and $μ={\rm const}$.
