论文标题
交错交错的su-schrieffer-heeger两链梯子的相图接近量子临界点
Phase diagram of an interacting staggered Su-Schrieffer-Heeger two-chain ladder close to a quantum critical point
论文作者
论文摘要
我们研究了高斯量子临界点附近相互作用的交错的su-schrieffer-heeger（SSH）梯子的地面相图。相应的有效场理论是双频正弦 - 戈登（DSG）模型，涉及在高斯固定点处的两个扰动：偏离临界和umklapp散射过程的偏差。仅考虑到非局部费米子场，奇偶校验和弦乐阶参数的考虑，热力学等效阶段之间的拓扑区别才变得可行。我们证明，非相互作用的效费用交错的SSH梯子完全等同于两个脱钩的Kitaev-Majorana链的O（2） - 对称模型，或两个1D P-WAVE超导体。当包括交互时，靠近高斯固定点，SSH梯子映射到Ashkin Teller类似系统。因此，SSH梯子中的拓扑顺序与相关的量子自旋链自由度的断裂对称阶段有关。获得的相图包括一个tomonaga-luttinger液态，由于umklapp过程，在自发性二聚化或电荷密度波的发作（CDW）上可能变得不稳定。在这些间隙阶段，基本体积激发是带有电荷QF = 1/2的量子扭结。对于足够强，远程相互作用，该模型的相图表现出高斯临界点的分叉为两个传出的伊斯汀关键。后一种三明治是混合阶段，其中二聚化与位点 - 划分CDW并存。在这个阶段，基本的体积激发由两种类型的拓扑孤子表示，载有不同的费米电荷，它们在0到1之间连续插入。该阶段还具有与共存的奇偶校验和弦序参数相混合的拓扑特性。
We study the ground-state phase diagram of an interacting staggered Su-Schrieffer-Heeger (SSH) ladder in the vicinity of the Gaussian quantum critical point. The corresponding effective field theory is a double-frequency sine-Gordon (DSG) model which involves two perturbations at the Gaussian fixed point: the deviation from criticality and Umklapp scattering processes. A topological distinction between thermodynamically equivalent phases becomes only feasible when nonlocal fermionic fields, parity and string order parameter, are included into consideration. We prove that a noninteracting fermionic staggered SSH ladder is exactly equivalent to a O(2)-symmetric model of two decoupled Kitaev-Majorana chains, or two 1D p-wave superconductors. Close to the Gaussian fixed point the SSH ladder maps to an Ashkin-Teller like system when interactions are included. Thus, the topological order in the SSH ladder is related to broken-symmetry phases of the associated quantum spin-chain degrees of freedom. The obtained phase diagram includes a Tomonaga-Luttinger liquid state which, due to Umklapp processes, can become unstable against either spontaneous dimerization or the onset of a charge-density wave (CDW). In these gapped phases elementary bulk excitations are quantum kinks carrying the charge QF = 1/2. For sufficiently strong, long-range interactions, the phase diagram of the model exhibits a bifurcation of the Gaussian critical point into two outgoing Ising criticalities. The latter sandwich a mixed phase in which dimerization coexists with a site-diagonal CDW. In this phase elementary bulk excitations are represented by two types of topological solitons carrying different fermionic charges, which continuously interpolate between 0 and 1. This phase has also mixed topological properties with coexisting parity and string order parameters.
