近日，福州大学的余雪佳及其研究团队取得一项新进展。经过不懈努力，他们揭示无间隙拓扑相之间的量子相变和临界行为。相关研究成果已于2024年6月27日在国际知名学术期刊《物理评论A》上发表。

在这项工作中，研究人员基于大规模密度矩阵重整群技术，研究了由Kennedy-Tasaki变换得到的扩展量子模型的临界行为。利用保真率作为诊断，研究人员得到了一个完整的相图，其中包括拓扑非平凡相和平凡无间隙相。此外，随着XXZ型向各向异性参数Δ的变化，临界点h_c和相关长度指数与Δ=0情况相同，其特征为=3/2 (伊辛 +自由玻色子)共形场理论。

这项研究结果表明，保真度磁化率能够精准地探测并揭示具有一般Δ值的不同无间隙拓扑相之间稳定的非传统临界线。此项工作为深入研究物质的无间隙拓扑相变提供了宝贵的参考。

据悉，间隙拓扑相之间的相变代表了一类超越朗道范式的非常规临界。然而，最近的研究已经将注意力转移到没有体隙的拓扑相上，其中它们之间的相变仍然很少见。

附：英文原文

Title: Quantum phase transition and critical behavior between the gapless topological phases

Author: Hao-Long Zhang, Han-Ze Li, Sheng Yang, Xue-Jia Yu

Issue&Volume: 2024/06/27

Abstract: The phase transition between gapped topological phases represents a class of unconventional criticality beyond the Landau paradigm. However, recent research has shifted attention to topological phases without a bulk gap, where the phase transitions between them are still elusive. In this work, based on large-scale density-matrix renormalization-group techniques, we investigate the critical behaviors of the extended quantum  XXZ model obtained by the Kennedy-Tasaki transformation. Using fidelity susceptibility as a diagnostic, we obtain a complete phase diagram, which includes both topological nontrivial and trivial gapless phases. Furthermore, as the XXZ-type anisotropy parameter Δ varies, both the critical points h_c and correlation length exponent remain the same as in the Δ=0 case, characterized by =3/2 (Ising plus free boson) conformal field theory. Our results indicate that fidelity susceptibility can effectively detect and reveal a stable unconventional critical line between the topologically distinct gapless phases for general Δ. This work serves as a valuable reference for further research on phase transitions within the gapless topological phase of matter.

DOI: 10.1103/PhysRevA.109.062226

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.109.062226