Nonmelting Disordering Facilitated by Electron Delocalization

Disordering atomic structures offers a functionality hardly expected in ordered states, including phase-change memory and photonic computing, offering the potential to renovate von Neumann architecture for neuromorphic engineering with low latency. However, significant energy consumption during the disordering compromises the data reliability and integration efficiency, which is traditionally regarded to take place after melting. Here, we investigate time for disordering in isochronal and isochoric manners, challenging the conventional melt-quenching theory. The disordering times of pure Sb, Ag-In-Sb-Te, and In surpass that of InSb by over 50 times, despite a higher melting point and a lower laser absorption rate of Sb compared to InSb. This nontrivial contrast is elucidated by theoretical calculation that delocalized electrons enable flexible modification of bond lengths even below the melting points where undermined bond directionality provides room for atoms to depart from their original positions. Facilitated by delocalized electrons, specifically through metavalent and metallic bonding rather than covalent bonding, atoms can be disordered without undergoing melting, which aligns with the rapid disordering of Sb compared to that of InSb. The results bridge the unaddressed gap between chemical interaction and kinetic behaviors during the disordering and suggest design rules highlighting electron-delocalization rather than solely relying on melting points to improve energy efficiency.