卤化物钙钛矿CsPbBr3中观测到的大姜-泰勒位移与分裂
Large Jahn-Teller shifts and splittings observed in halide perovskite CsPbBr3
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中文总结 AI 辅助
本研究在CsPbBr3中观测到姜-泰勒效应相关的能带位移与分裂，关联其与PbBr6八面体畸变的关系，揭示了卤化物钙钛矿的强电子-晶格相互作用。
中文摘要 AI 辅助
尽管一阶和二阶姜-泰勒效应对塑造材料结构与电子性质具有基础性作用，但在固体角分辨光电子能谱中却鲜有相关观测报道。在氧化物和卤化物钙钛矿中，能带结构的副本曾被偶尔报道为姜-泰勒效应的指纹，但伴随的能量位移或分裂却从未被观测到，而这类观测本可用于确定其起源。在CsPbBr3中，我们揭示了两类关键特征：冷却过程中，正交晶系的副本能带出现，而这一现象此前的研究并未观测到，其中包括在Γ点处的额外价带极大值，甚至在室温下也可被区分。最重要的是，沿Γ-M方向的能带窄化、Γ点处的分裂，以及非等价M点间简并度的解除，所有这些效应的量级均为数百meV。将温度依赖的X射线衍射作为能带结构计算的输入，我们将这些效应直接与PbBr6八面体的倾斜和旋转关联起来。我们的研究结果揭示了卤化物钙钛矿中强电子-晶格相互作用，这一相互作用是解决目前尚未解决的极化子输运、动态无序以及激子俘获等问题的核心。
英文摘要
Despite the fundamental role of Jahn-Teller effects of first and second order in shaping structural and electronic properties, there is hardly any observation in angle-resolved photoemission of solids. In oxide and halide perovskites, band structure replicas have occasionally been reported as fingerprints of Jahn-Teller effects, but no accompanying energy shifts or splittings that would allow a conclusion about their origin. In CsPbBr3, we uncover both key signatures: Upon cooling, orthorhombic replica bands emerge which had eluded earlier studies. This includes an extra valence band maximum at Γ which can even be distinguished at room temperature. Most importantly, band narrowing along Γ-M, a splitting at Γ, and the lifting of degeneracy between nonequivalent M points, all of several 100 meV, become apparent. Temperature-dependent x-ray diffraction, used as input for band structure calculations, links these effects directly to tilts and rotations of the PbBr6 octahedra. Our results uncover a strong electron-lattice interaction which is at the heart of so-far unresolved questions concerning polaronic transport, dynamic disorder, and exciton trapping in halide perovskites.
