Excited-state quantum phase transitions extend the transition concept beyond ground state and offer insights into complex behavior of systems. In present work we assess use multiple coherence spectrum as a valid tool to probe excited-state within framework Lipkin-Meshkov-Glick model. The time dependence long-time average reveal intricate dynamics that stems from existence singularities in many-body system. Published by American Physical Society 2025

We present an extension of the Hamiltonian two dimensional limit vibron model encompassing all possible interactions up to four-body operators. apply this modeling experimental bending spectrum fourteen molecules. The degrees freedom selected molecular species include situations: linear, bent, and nonrigid equilibrium structures; demonstrating flexibility algebraic approach, that allows for consideration utterly different physical cases with a general formalism single Hamiltonian. For each...

We characterize excited state quantum phase transitions in the two dimensional limit of vibron model with fidelity susceptibility, comparing obtained results information provided by participation ratio. As an application, we locate eigenstate closest to barrier linearity and determine linear or bent character different overtones for particular bending modes six molecular species. perform a fit use optimized eigenvalues eigenstates three cases make recently published other cases.

The basic Lipkin-Meshkov-Glick model displays a second-order ground-state quantum phase transition and an excited-state (ESQPT). inclusion of anharmonic term in the Hamiltonian implies second ESQPT different nature. We characterize this using mean field limit model. alternative ESQPT, associated with changes boundary finite Hilbert space system, can be properly described order parameter transition, energy gap between adjacent states, participation ratio, fidelity susceptibility.

Recent works have shown that the spectroscopic access to highly excited states provides enough information characterize transition in isomerization reactions. Here, we show about state of bond-breaking HCN–HNC reaction can also be achieved with two-dimensional limit algebraic vibron model. We describe system's bending vibration Hamiltonian and use its classical state. Using either coherent formalism or a recently proposed approach by Baraban [ Science 2015, 350, 1338–1342], obtain an...

In most cases, excited-state quantum phase transitions can be associated with the existence of critical points (local extrema or saddle points) in a system's classical limit energy functional. However, an transition might also stem from lowering asymptotic corresponding One such example occurs two-dimensional (2D) vibron model, once anharmonic term form quadratic bosonic number operator is added to Hamiltonian. This case has been studied broken-symmetry [P\'erez-Bernal and \'Alvarez-Bajo,...

The standard Lipkin-Meshkov-Glick (LMG) model undergoes a second-order ground-state quantum phase transition (QPT) and an excited-state (ESQPT). inclusion of anharmonic term in the LMG Hamiltonian gives rise to second ESQPT that alters static properties [Gamito , Phys. Rev. E 106, 044125 (2022)]. In present work, dynamical implications associated this new are analyzed. For purpose, quench protocol is defined on system takes initial state, usually ground into complex excited state evolves...

Excited-state quantum phase transitions (ESQPTs) strongly influence the spectral properties of collective many-body systems, changing degeneracy patterns in different phases. Level degeneracies turn affect system's dynamics. We analyze dependence on size two-level boson models with a $u(n+1)$ dynamical algebra, where $n$ is number degrees freedom. Below ESQPT critical energy these models, gap between neighboring levels that belong to symmetry sectors gets close zero as system increases....

Quantum phase transitions encompass a variety of phenomena that occur in quantum systems exhibiting several possible symmetries. Traditionally, these are explored by continuously varying control parameter connects two different symmetry configurations. Here we propose an alternative approach where the undergoes abrupt and time-periodic jumps between only values. This yields results surprisingly similar to those obtained traditional one may prove experimentally useful situations accessing is...

The basic Lipkin-Meshkov-Glick model displays a second order ground state quantum phase transition and an excited (ESQPT). inclusion of anharmonic term in the Hamiltonian implies ESQPT different nature. We characterize this using mean field limit model. new ESQPT, associated with changes boundary finite Hilbert space system, can be properly described parameter transition, energy gap between adjacent states, participation ratio, fidelity susceptibility.

Excited-state quantum phase transitions (ESQPTs) strongly influence the spectral properties of collective many-body systems, changing degeneracy patterns in different phases. Level degeneracies, turn, affect system's dynamics. We analyze dependence on size two-level boson models with a $u(n+1)$ dynamical algebra, where $n$ is number degrees freedom. Below ESQPT critical energy these models, gap between neighboring levels that belong to symmetry sectors gets close zero as system increases....

The standard Lipkin-Meshkov-Glick (LMG) model undergoes a second-order ground-state quantum phase transition (QPT) and an excited-state (ESQPT). inclusion of anharmonic term in the LMG Hamiltonian gives rise to second ESQPT that alters static properties [Phys. Rev. E 106, 044125 (2022)]. In present work, dynamical implications associated this new are analyzed. For purpose, quench protocol is defined on system takes initial state, usually ground into complex excited state evolves time. impact...

Molecular bending spectra can be broadly categorized into three physical cases, depending on the molecular equilibrium configuration: linear, bent, and nonrigid.We have studied cases in detail with an extended Hamiltonian (including up to four-body interactions) of 2D limit Vibron Model (2DVM).We obtained band origin predictions within experimental accuracy as well corresponding eigenstates for several molecules a .The particular spectroscopic signatures characterizing states that straddle...