平带固体中热点呼吸声子驱动的巨带隙脉动
Giant Bandgap Pulsation Driven by Hotspot Breathing Phonons in a Flat-Band Solid
中文总结 AI 辅助
该研究通过从头算分子动力学等方法，发现类钙钛矿平带固体中A₁g类呼吸声子驱动室温下约7.8 THz、峰峰值近0.95 eV的巨带隙脉动，揭示了无序热涨落中可产生有序电子响应。
中文摘要 AI 辅助
固体的电子带隙在给定温度下通常被视为静态属性，在平衡条件下仅存在微弱且随机的热涨落。本文利用从头算分子动力学和第一性原理电声耦合计算，在一种类钙钛矿平带固体中发现了室温下约7.8 THz的显著带隙脉动，其最大峰峰值变化接近0.95 eV。该行为源于双重选择机制：A₁g类呼吸支与平带导带边的耦合强度远大于其他声子支，而实空间相位选择性区分了其热点Γ点和有限q分量。尽管有限q模式保留了可观的微观耦合，但其晶胞间相移产生的响应振幅更小、重复周期更短，使晶胞同步的Γ点A₁g分量成为基频带隙脉动的主导因素。由此产生的带边动力学进一步在飞秒时间尺度上调制光学响应。这些发现表明，从本质上无序的热晶格涨落中可以出现出乎意料的有序电子响应。
英文摘要
The electronic bandgap of solids is conventionally viewed as a static property at a given temperature, with only weak and stochastic thermal fluctuations under equilibrium conditions. Here, using ab initio molecular dynamics and first-principles electron-phonon calculations, we reveal a pronounced room-temperature bandgap pulsation at about 7.8 THz in a perovskite-like flat-band solid, with a maximum peak-to-peak variation approaching 0.95 eV. This behavior originates from a dual selection mechanism: the A1g-like breathing branch couples much more strongly to the flat conduction-band edge than other phonon branches, while real-space phase selectivity distinguishes its hotspot gamma-point and finite-q components. Although finite-q modes retain appreciable microscopic coupling, their intercell phase shifts produce smaller-amplitude shorter-recurrence-period responses, leaving the unit-cell-synchronous gamma-point A1g component to dominate the fundamental-period bandgap pulsation. The resulting band-edge dynamics further modulates the optical response on femtosecond timescales. These findings demonstrate that an unexpectedly ordered electronic response can emerge from intrinsically disordered thermal lattice fluctuations.
