Related Experiment Video
Updated: Aug 20, 2025
08:04
Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids
Published on: May 27, 2020
8.5K
Excited-state quantum phase transitions in the anharmonic Lipkin-Meshkov-Glick model: Static aspects
J Gamito1, J Khalouf-Rivera2, J M Arias1,3
1Departamento de Física Atómica, Molecular y Nuclear, Facultad de Física, Universidad de Sevilla, Apartado 1065, 41080 Sevilla, Spain.
Physical Review. E
|November 18, 2022
Summary
The Lipkin-Meshkov-Glick model exhibits two quantum phase transitions. An anharmonic term introduces a second excited-state quantum phase transition (ESQPT) characterized by specific parameters.
Area of Science:
- Quantum Many-Body Physics
- Quantum Phase Transitions
- Statistical Mechanics
Background:
- The Lipkin-Meshkov-Glick (LMG) model is a fundamental model in quantum many-body physics.
- It exhibits both ground-state quantum phase transitions (GSQPT) and excited-state quantum phase transitions (ESQPT).
Purpose of the Study:
- To investigate the nature of a second, distinct ESQPT introduced by an anharmonic term in the LMG model.
- To characterize this alternative ESQPT using various physical observables.
Main Methods:
- Analysis of the LMG model with an added anharmonic term in the Hamiltonian.
- Employing the mean-field limit for characterization.
- Utilizing the ground-state quantum phase transition order parameter.
- Examining the energy gap between adjacent states.
- Calculating the participation ratio.
- Assessing quantum fidelity susceptibility.
Main Results:
- The inclusion of an anharmonic term leads to a second ESQPT with different characteristics.
- This alternative ESQPT is associated with changes at the boundary of the finite Hilbert space.
- The study successfully characterizes this ESQPT using established and advanced quantum measures.
Conclusions:
- The anharmonic LMG model presents a novel type of ESQPT.
- The identified ESQPT can be effectively described by analyzing the ground-state order parameter, energy gap, participation ratio, and quantum fidelity susceptibility.
Related Concept Videos
02:31Phase Transitions
19.5K
Whether solid, liquid, or gas, a substance's state depends on the order and arrangement of its particles (atoms, molecules, or ions). Particles in the solid pack closely together, generally in a pattern. The particles vibrate about their fixed positions but do not move or squeeze past their neighbors. In liquids, although the particles are closely spaced, they are randomly arranged. The position of the particles are not fixed—that is, they are free to move past their neighbors to...
19.5K
01:23Atomic Nuclei: Nuclear Relaxation Processes
701
In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis, the precessing magnetic moments are randomly oriented around the z-axis.
701
02:39Phase Transitions: Melting and Freezing
12.6K
Heating a crystalline solid increases the average energy of its atoms, molecules, or ions, and the solid gets hotter. At some point, the added energy becomes large enough to partially overcome the forces holding the molecules or ions of the solid in their fixed positions, and the solid begins the process of transitioning to the liquid state or melting. At this point, the temperature of the solid stops rising, despite the continual input of heat, and it remains constant until all of the solid is...
12.6K
02:39Phase Transitions: Vaporization and Condensation
17.8K
The physical form of a substance changes on changing its temperature. For example, raising the temperature of a liquid causes the liquid to vaporize (convert into vapor). The process is called vaporization—a surface phenomenon. Vaporization occurs when the thermal motion of the molecules overcome the intermolecular forces, and the molecules (at the surface) escape into the gaseous state. When a liquid vaporizes in a closed container, gas molecules cannot escape. As these gas phase...
17.8K
00:59States of Matter and Phase Changes
1.2K
The internal energy of a substance—the total kinetic energy of all its molecules and the potential energy of their associated forces—depends on the strength of the intermolecular forces in the condensed phases and the pressure exerted on the substance. The internal energy of a substance is the highest in the gaseous state, the lowest in the solid state, and intermediate in the liquid state. Phase transitions are caused by changes in physical conditions, such as temperature and...
1.2K
01:16UV–Vis Spectroscopy: Molecular Electronic Transitions
1.7K
In Ultraviolet–Visible (UV–Vis) spectroscopy, the absorption of electromagnetic radiation is used to probe the electronic structure of molecules. This technique provides insights into molecular electronic transitions, particularly the movement of electrons between different molecular orbitals. Radiation is absorbed if the energy of the electromagnetic radiation passing through the molecule is precisely equal to the energy difference between the excited and ground states. During this...
1.7K