2024/08/22 by Moon, Jaeyun, Leo Zella, Lucas Lindsay +2
Materials Science · #Condensed matter physics #FOS: Physical sciences #Harmonic #Harmonic oscillator #Materials Science (cond-mat.mtrl-sci) #Phonon #Physics #Quantum mechanics #Thermal properties of materials
paper · pdf · doi:10.48550/arxiv.2408.12467
openalex publication_date 2024/08/22 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
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.