近日，中国工程物理研究院流体物理研究所的覃睿与四川大学的陈自宇合作并取得一项新进展。经过不懈努力，他们对单层黑磷拓扑相变中角相关高次谐波的产生进行研究。相关研究成果已于2024年4月1日在国际知名学术期刊《物理评论A》上发表。

据悉，确定全光高次谐波观测值作为探测物质拓扑结构的可靠特征引起了人们的强烈兴趣。最近，大量的从头计算模拟挑战了先前探索的方法，并提出了一个新的潜在特征，即谐波产率的角依赖性，作为材料拓扑的可能指纹。然而，来自能带结构、自旋轨道耦合(SOC)和贝里曲率的非拓扑贡献并没有被排除。

为了澄清这一疑问，该研究团队精心选择了单层黑磷样品系统作为研究对象。该系统具有相似的带结构，并且在应变诱导的平凡相和拓扑相中，均不存在自旋轨道耦合（SOC）和贝里曲率效应。经过深入研究，研究人员发现先前提出的角相关谐波差已经消失，这表明它并不是一个可靠的观测值，无法准确探测材料的拓扑性质。

附：英文原文

Title: Angle-dependent high-order harmonic generation in a topological phase transition of monolayer black phosphorous

Author: Rui Qin, Zi-Yu Chen

Issue&Volume: 2024/04/01

Abstract: Identifying all-optical high-order harmonic observables as reliable signatures to probe the topology of matter has triggered intense interest. Recently, extensive ab initio simulations challenged the previously explored approaches and proposed a new potential feature, i.e., angular dependence of harmonic yield, as a possible fingerprint of material topology [O. Neufeld et al., Phys. Rev. X 13, 031011 (2023)]. However, nontopological contributions from the band structure, spin-orbit coupling (SOC), and Berry curvature have not been ruled out. Here, we clarify this point by studying the elaborately chosen sample system of monolayer black phosphorus, which exhibits similar band structures and are free from SOC as well as Berry curvature effects for both the trivial and topological phases induced by strain. We find the previously proposed angle-dependent harmonic difference to vanish, suggesting it to be an unreliable observable to probe material topology.

DOI: 10.1103/PhysRevA.109.043102

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.109.043102