半导体石墨烯纳米带的非线性光学响应：隐藏对称性的强约束

中文摘要 AI 辅助

非线性光学（NLO）响应是探测材料结构的强大工具，因为它们对空间对称性高度敏感。例如，众所周知，具有反演对称性会禁止偶数阶NLO效应。在这里，我们展示了非空间对称性也能显著约束NLO响应。在具有二部晶格结构的石墨烯纳米带（GNRs）中，我们确定了近似的二部晶格粒子-空穴（BLPH）对称性强烈抑制偶数阶NLO效应，即使对于没有反演对称性的系统也是如此。重要的是，我们证明了这种近似对称性使得在铁磁性GNRs中能够光学产生近乎纯净的自旋位移电流，而电荷位移电流被强烈抑制。这些光诱导直流自旋电流的自旋方向可以通过外部磁场轻松调节，为在反铁磁系统中产生纯自旋位移电流的先前方案提供了明显优势。我们使用最近合成的铁磁性Janus GNR来说明我们的发现。我们的结果强调了NLO响应中被忽视的对称性方面的重要性，并突出了磁性GNRs作为自旋电子器件有前景的候选材料。

英文摘要

Nonlinear optical (NLO) responses are powerful tools for probing material structures, as they are highly sensitive to spatial symmetries. For instance, it is well known that having inversion symmetry forbids even-order NLO effects. Here, we show that nonspatial symmetries can also significantly constrain NLO responses. In graphene nanoribbons (GNRs) with bipartite-lattice structures, we identify the approximate bipartite-lattice particle-hole (BLPH) symmetry strongly suppresses even-order NLO effects, even for systems with no inversion symmetry. Importantly, we demonstrate that this approximate symmetry enables the optical generation of nearly pure spin shift currents in ferromagnetic GNRs, with the charge shift currents strongly suppressed. The spin orientation of these photo-induced DC spin currents can be easily tuned by an external magnetic field, providing distinct advantages over previous schemes for generating pure spin shift currents in antiferromagnetic systems. We illustrate our findings using a recently synthesized ferromagnetic Janus GNR. Our results underscore the significance of an overlooked symmetry aspect of NLO responses and highlight magnetic GNRs as promising candidates for spintronic devices.

发表机构

• University of California at Berkeley（加州大学伯克利分校）
• Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）
• Eastern Institute of Technology（宁波东方理工大学）
• National Center of Theoretical Sciences（台湾理论科学中心）
• Institute of Atomic and Molecular Sciences, Academia Sinica（中央研究院原子与分子科学研究所）

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