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

Keiichiro Nasu

doi:10.3390/app8030332

Abstract

Real time quantum dynamics of the spontaneous translational symmetry breakage in the early stage of photo-induced 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, which is 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? No! 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.

Highlights

The spontaneous symmetry breakage is one of the most important problems of great interest in the solid state physics for these several decades
Sci. 2018, 8, 332 real time quantum dynamics of optically created electronic excitations is gradually clarified in detail up to a pico- or femto-second time scale
At the FC state, an electronic excitation that is just created by a visible light is in a plane wave state, extended all over the crystal

Summary

Introduction

The spontaneous symmetry breakage is one of the most important problems of great interest in the solid state physics for these several decades. We determine the real value of this hypothetical finite unequal occupation, so that it will give the lowest free energy If this lowest energy is even lower than the starting paramagnetic state, without an externally applied magnetic field, we can get a ferromagnetic state that has a spontaneous and macroscopic magnetic (spin) moment. Sci. 2018, 8, 332 real time quantum dynamics of optically created electronic excitations is gradually clarified in detail up to a pico- or femto-second time scale This advantageous experimental technology has been intensively applied even to the present spontaneous symmetry breaking problem. It is nothing but the spontaneous translational symmetry breakage This self-localized exciton still remains within the energy gap of the original insulating crystal, and it is luminescent. It was once reviewed only shortly [12], and the explanation was quite insufficient

Adiabatic Nature of Exciton Self-Localization

Dynamics of Self-Localization

The schematic nature of of thethe decrease ofof spatial correlation

Conclusions