几十年来，声子准粒子在微观上理解凝聚态物质的热力学和输运性质方面具有里程碑意义。声子与简谐本征态有一一对应关系，其能量通常由简单的独立简谐振子模型描述。势能中的高阶项导致它们之间的相互作用，即使在完美晶体中也会产生有限的寿命和频移。然而，越来越多的证据（包括不同于预期 Dulong-Petit 定律的定容热容）表明需要重新评估具有简谐能量的声子。在这项工作中，我们通过能量协方差计算，明确检验了原型晶体硅的声子能量的模间依赖性，并证明了即使在 300 K 下声子能量的协同性质，这质疑了热力学和输运的声子能量描述中通常使用的独立简谐振子假设。
英文摘要：
Phonon quasi-particles have been monumental in microscopically understanding thermodynamics and transport properties in condensed matter for decades. Phonons have one-to-one correspondence with harmonic eigenstates and their energies are often described by simple independent harmonic oscillator models. Higher order terms in the potential energy lead to interactions among them, resulting in finite lifetimes and frequency shifts, even in perfect crystals. However, increasing evidence including constant volume heat capacity different from the expected Dulong-Petit law suggests the need for re-evaluation of phonons having harmonic energies. In this work, we explicitly examine inter-mode dependence of phonon energies of a prototypical crystal, silicon, through energy covariance calculations and demonstrate the concerted nature of phonon energies even at 300 K, questioning independent harmonic oscillator assumptions commonly used for phonon energy descriptions of thermodynamics and transport.
Spontaneous Symmetry Breaking and Collective Higgs-Goldstone Dynamics in Solid-State Phononic Frequency Combs
Birla Institute of Technology and Science, Pilani - Dubai Campus（比拉理工学院，皮拉尼-迪拜校区）；Birla Institute of Technology and Science, Pilani - Pilani Campus（比拉理工学院，皮拉尼-皮拉尼校区）
Collective Phonon Mixing and Eigenvector Transport Under Isotope Substitution
ISIS Neutron and Muon Source, STFC, Rutherford Appleton Laboratory（STFC拉瑟福德阿普尔顿实验室中子与μ子源）；University of Bath（巴斯大学）；United Kingdom Atomic Energy Authority（英国原子能管理局）
