Quantum dynamics of localized excitations in a symmetric trimer molecule

TL;DR

This paper investigates the quantum dynamics of localized excitations in a symmetric trimer molecule, revealing conditions for persistent localization due to spectral degeneracies and tunneling suppression.

Contribution

It introduces a detailed analysis of how spectral degeneracies affect the tunneling and localization of excitations in a quantum trimer, highlighting new degeneracy phenomena.

Findings

Degeneracy points cause tunneling suppression.

Localized excitations can remain indefinitely localized.

Spectral overlaps influence dynamical properties.

Abstract

We study the time evolution of localized (local bond) excitations in a symmetric quantum trimer molecule. We relate the dynamical properties of localized excitations such as their spectral intensity and their temporal evolution (survival probability and tunneling of bosons) to their degree of overlap with quantum tunneling pair states. We report on the existence of degeneracy points in the trimer eigenvalue spectrum for specific values of parameters due to avoided crossings between tunneling pair states and additional states. The tunneling of localized excitations which overlap with these degenerate states is suppressed on all times. As a result local bond excitations may be strongly localized forever, similar to their classical counterparts.