Degenerate Quantum States as Key Drivers of Sudden Thermomechanical Transitions

Quantum degeneracies in solids are fundamental to electronic behavior and thermodynamic stability. However, their role under thermomechanical compression remains poorly understood. This study, combining non-perturbative electron-phonon calculations with interactive visualization techniques, reveals that the interplay between quantum degeneracies and electron-phonon interactions drives pressure-induced ultrafast chemical transformations. Specifically, degenerate quantum states at the Fermi level dynamically enhance electron-phonon coupling, inducing an attractive interaction that opens a gap and lowers the ground state energy. This mechanism dictates the reaction pathway for the rapid transformation of graphite into hexagonal diamond under compression. Furthermore, the reaction mode—dominated by the optical phonon mode—is fully determined by the graphite crystal structure, with its frequency exhibiting near-independence from vibrational wavenumber. The Einstein model provides a more accurate framework for predicting transformation temperatures and pressures, aligning closely with experimental results. Analogous to superconductivity, where electron-phonon interactions create an energy gap, this study demonstrates how quantum degeneracies influence macroscopic thermomechanical transformations, offering new insights into a novel quantum-driven thermomechanical phenomenon.