AI 中文总结
该研究利用边界驱动SSH链的非平衡稳态对称性破缺，在不修改哈密顿量的情况下实现偶次谐波产生，建立了输运电流与HHG选择定则的关联，为探测中心对称系统输运电流提供了新方法。
AI 中文摘要
在具有反演对称性的系统中，高次谐波产生（HHG）通常受对称性限制仅能产生奇次谐波。本文证明，无需修改 underlying 哈密顿量即可打破该选择定则。我们研究了耦合到源和漏库的边界驱动Su-Schrieffer-Heeger（SSH）链，证明耗散动力学可产生携带有限直流电流的非平衡稳态。尽管SSH哈密顿量保留反演对称性，但载流稳态密度矩阵不具备该对称性，导致发射光谱中出现偶次谐波。利用基于Lindblad主方程的关联矩阵方法，我们得到了该稳态并计算了对应的HHG响应。我们发现偶次谐波的强度由输运电流直接控制，建立了非平衡电荷输运与HHG选择定则之间的关联。研究揭示了一种仅依赖非平衡稳态对称性破缺的偶次谐波产生机制，为通过中心对称量子系统中的超快非线性光谱探测输运电流提供了途径。
英文摘要
High-harmonic generation (HHG) in inversion-symmetric systems is typically restricted to odd harmonics by symmetry. Here, we show that this selection rule can be broken without modifying the underlying Hamiltonian. We investigate a boundary-driven Su-Schrieffer-Heeger (SSH) chain coupled to source and sink reservoirs and demonstrate that dissipative dynamics generates a nonequilibrium steady state carrying a finite DC current. While the SSH Hamiltonian retains inversion symmetry, the current-carrying steady-state density matrix does not, leading to the emergence of even harmonics in the emitted spectrum. Using a correlation-matrix approach based on the Lindblad master equation, we obtain the steady state and calculate the resulting HHG response. We find that the intensity of the even harmonics is directly controlled by the transport current, establishing a link between nonequilibrium charge transport and HHG selection rules. Our results uncover a mechanism for even-harmonic generation that relies solely on nonequilibrium steady-state symmetry breaking and provide a route to probing transport currents through ultrafast nonlinear spectroscopy in centrosymmetric quantum systems.
Comments13 pages, 5 figures, revtex4-2
