超宽禁带SrSnO3中的四声子散射与相干热输运
Four-phonon scattering and coherent heat transport in ultrawide-bandgap SrSnO3
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中文总结 AI 辅助
本文结合第一性原理方法，揭示四声子散射与相干输运对超宽禁带SrSnO3晶格热导率的关键作用，修正了仅用三声子描述热输运的不足，为强畸变氧化物的非谐热输运研究提供了基准。
中文摘要 AI 辅助
SrSnO3是一种极具前景的超宽禁带钙钛矿氧化物，其热输运由结构畸变与非谐晶格动力学主导。本文在统一的第一性原理框架内研究正交相和立方相SrSnO3的晶格热导率（κL），该框架结合了自洽声子重整化、三声子与四声子散射以及相干热输运。键合分析显示，刚性Sn-O八面体骨架嵌入弱键合的Sr亚晶格中，产生易受强非谐效应影响的低频振动模式。四声子散射被确定为限制粒子型热传导的关键机制，在300 K时使正交相的Peierls热导率降低19.4%，在1300 K时使立方相的该值降低52.1%，而相干贡献提供了有限的通道，部分补偿了这种降低。我们进一步表明，室温下三声子计算结果与实验热导率的表观一致性并非完整物理描述的体现，而是源于四声子对粒子型通道的抑制与被忽略的相干贡献之间的近乎抵消。当考虑完整温度依赖性时，这种抵消会消失，只有综合处理才能提高与实验观测到的标度行为的一致性。因此，对κL的物理一致描述需要同等处理声子重整化、四声子散射和相干输运，而非从单一温度下三声子计算的一致性中推断。这些结果为超宽禁带锡酸盐钙钛矿的热输运提供了微观视角，并为强畸变氧化物中的非谐输运建立了基准。
英文摘要
SrSnO3 is a promising ultrawide-bandgap perovskite oxide whose thermal transport is governed by structural distortions and anharmonic lattice dynamics. Here, we investigate the lattice thermal conductivity (kL) of orthorhombic and cubic SrSnO3 within a unified first-principles framework combining self-consistent phonon renormalization, three- and four-phonon scattering, and coherent heat transport. Bonding analysis reveals a rigid Sn-O octahedral framework embedded in a weakly bonded Sr sublattice, giving rise to low-frequency vibrational modes susceptible to strong anharmonic effects. Four-phonon scattering is identified as a key mechanism limiting particle-like heat conduction, reducing the Peierls thermal conductivity by 19.4% at 300 K in the orthorhombic phase and by 52.1% at 1300 K in the cubic phase, while the coherent contribution provides a finite channel that partially compensates this reduction. We further show that the apparent agreement between three-phonon calculations and experimental thermal conductivity at room temperature is not indicative of a complete physical description. Instead, it arises from a near cancellation between four-phonon suppression of the particle-like channel and the neglected coherent contribution. This cancellation breaks down when the full temperature dependence is considered, where only the combined treatment improves agreement with the experimentally observed scaling behavior. A physically consistent description of kL therefore requires phonon renormalization, four-phonon scattering, and coherent transport to be treated on equal footing rather than inferred from three-phonon agreement at a single temperature. These results provide microscopic insight into thermal transport in ultrawide-bandgap stannate perovskites and establish a benchmark for anharmonic transport in strongly distorted oxides.
