Real Time Quantum Dynamics of Spontaneous Translational Symmetry Breakage in the Early Stage of Photo-induced Structural Phase Transitions

TL;DR

This paper reviews the real-time quantum dynamics of spontaneous translational symmetry breaking during early photo-induced structural phase transitions, emphasizing the role of quantum coherence loss without wave function shrinkage.

Contribution

It provides a theoretical explanation based on Toyozawa theory for the quantum dynamics of symmetry breaking in photoinduced phase transitions, consistent with conservation laws.

Findings

Quantum coherence disappears during lattice relaxation.

Wave function does not shrink, but coherence is lost.

Symmetry breaking is driven by coherence loss, not wave function collapse.

Abstract

Real time quantum dynamics of the spontaneous translational symmetry breakage in the early stage of photoinduced structural phase transitions is reviewed and supplementally explained, under the guide of the Toyozawa theory, which is exactly in compliance with the conservation laws of the total momentum and energy. At the Franck Condon state, an electronic excitation just created by a visible light, is in a plane wave state, extended all over the crystal. While, after the lattice relaxation having been completed, it is localized around a certain lattice site of the crystal, as a new excitation. Is there a sudden shrinkage of the excitation wave function, in between. The wave function never shrinks, but only the spatial, or inter lattice site quantum coherence, interference of the excitation disappears, as the lattice relaxation proceeds. This is nothing but the spontaneous breakage of translational symmetry.