Quantum fidelity susceptibility in excited state quantum phase transitions: application to the bending spectra of nonrigid molecules

TL;DR

This paper uses quantum fidelity susceptibility to analyze excited state quantum phase transitions in molecular bending spectra, providing a novel approach to characterize molecular vibrational states and their phase transition behavior.

Contribution

It introduces the use of quantum fidelity susceptibility for excited state quantum phase transitions and applies it to molecular vibrational data with a four-body algebraic Hamiltonian.

Findings

Identifies eigenstates near the barrier to linearity in molecules.

Distinguishes linear and bent vibrational overtones.

Provides a new method for analyzing molecular phase transitions.

Abstract

We characterize excited state quantum phase transitions in the two dimensional limit of the vibron model with the quantum fidelity susceptibility, comparing the obtained results with the information provided by the participation ratio. As an application, we perform fits using a four-body algebraic Hamiltonian to bending vibrational data for several molecular species and, using the optimized eigenvalues and eigenstates, we locate the eigenstate closest to the barrier to linearity and determine the linear or bent character of the different overtones.