AI 中文总结
结合光学SHG等技术，揭示KTaO3中氧缺陷介导的非线性通道与软极性模式耦合的声子机制，修正反演对称性破缺温度依赖表现的传统图像，建立缺陷介导非线性响应的研究框架。
AI 中文摘要
对称性是凝聚态物理的基础，其实验表现为理解量子材料的集体行为提供了根本视角。光学二次谐波产生（SHG）被广泛视为反演对称性破缺的指纹，但集体晶格动力学是否以及如何调控局域反演对称性破缺的非线性光学表现仍属未知。本文结合光学SHG、漫散射X射线及微观理论，揭示了调控量子顺电材料KTaO3中局域反演对称性破缺的温度依赖表现的声子机制。研究表明，氧缺陷介导的非线性光学通道与基体软极性模式强耦合，该模式的热波动会扰乱相关电子相位相干性，从而在温度升高时抑制局域反演对称性破缺的非线性表现。因此，非线性响应呈现出由局域反演对称性破缺在光学上可表现的状态向有效中心对称状态的温度驱动交叉，且无伴随结构变化。这些发现修正了量子顺电体中反演对称性破缺的温度依赖表现的传统图像，建立了理解和设计含低能极性激发的材料中缺陷介导的非线性光学响应的框架。
英文摘要
Symmetry lays the foundation of condensed matter physics and its experimental manifestation provides fundamental insight into the collective behaviors of quantum materials. Optical second-harmonic generation (SHG) is widely regarded as a fingerprint of inversion-symmetry breaking, yet whether and how collective lattice dynamics govern the nonlinear optical manifestation of local inversion-symmetry breaking remains unknown. Here, combining optical SHG, diffuse X-ray scattering, and microscopic theory, we reveal a phonon-regulated mechanism governing the temperature-dependent manifestation of local inversion-symmetry breaking in quantum paraelectric material KTaO3. We demonstrate that an oxygen-defect-mediated nonlinear optical channel is strongly coupled to the host soft polar mode, whose thermal fluctuations scramble the associated electronic phase coherence and thereby suppress the nonlinear manifestation of local inversion-symmetry breaking at elevated temperatures. Consequently, the nonlinear response exhibits a temperature-driven crossover from a regime in which local inversion-symmetry breaking is optically manifest to one that appears effectively centrosymmetric, without any accompanying structural change. Our findings revise the conventional picture of the temperature-dependent manifestation of inversion-symmetry breaking in quantum paraelectrics and establish a framework for understanding and engineering defect-mediated nonlinear optical responses in materials hosting low-energy polar excitations.
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