Complete analysis of ensemble inequivalence in the Blume-Emery-Griffiths model
| Autor: | Alessandro Campa, V. V. Hovhannisyan, Nerses Ananikian, Stefano Ruffo |
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| Rok vydání: | 2017 |
| Předmět: |
Phase transition
Paramagnetic phasis Singularity theory Triple point Paramagnetic phase FOS: Physical sciences 01 natural sciences Condensed Matter::Disordered Systems and Neural Networks 010305 fluids & plasmas Settore FIS/03 - Fisica della Materia Ensemble inequivalence Blume-Emery-Griffiths model Critical point (thermodynamics) 0103 physical sciences Canonical ensemble Microcanonical ensembles Statistical physics 010306 general physics Mean-Field Model Condensed Matter - Statistical Mechanics Mathematics Phase diagram Blume-Emery-Griffiths model Statistical Mechanics (cond-mat.stat-mech) Long-range Interactions Ensemble inequivalence Biquadratic exchange Settore FIS/02 - Fisica Teorica Modelli e Metodi Matematici Microcanonical ensemble Tricritical point Second-order phase transition Microcanonical Ensemble Condensed Matter::Statistical Mechanics |
| Zdroj: | Physical review. E, Statistical, nonlinear and soft matter physics (Online) 96 (2017): 062103-1–062103-19. doi:10.1103/PhysRevE.96.062103 info:cnr-pdr/source/autori:Hovhannisyan V.V.; Ananikian N.S.; Campa A.; Ruffo S./titolo:Complete analysis of ensemble inequivalence in the Blume-Emery-Griffiths model/doi:10.1103%2FPhysRevE.96.062103/rivista:Physical review. E, Statistical, nonlinear and soft matter physics (Online)/anno:2017/pagina_da:062103-1/pagina_a:062103-19/intervallo_pagine:062103-1–062103-19/volume:96 |
| ISSN: | 2470-0053 |
| DOI: | 10.1103/PhysRevE.96.062103 |
| Popis: | We study inequivalence of canonical and microcanonical ensembles in the mean-field Blume-Emery-Griffiths model. This generalizes previous results obtained for the Blume-Capel model. The phase diagram strongly depends on the value of the biquadratic exchange interaction K, the additional feature present in the Blume-Emery-Griffiths model. At small values of K, as for the Blume-Capel model, lines of first and second order phase transitions between a ferromagnetic and a paramagnetic phase are present, separated by a tricritical point whose location is different in the two ensembles. At higher values of K the phase diagram changes substantially, with the appearance of a triple point in the canonical ensemble which does not find any correspondence in the microcanonical ensemble. Moreover, one of the first order lines that starts from the triple point ends in a critical point, whose position in the phase diagram is different in the two ensembles. This line separates two paramagnetic phases characterized by a different value of the quadrupole moment. These features were not previously studied for other models and substantially enrich the landscape of ensemble inequivalence, identifying new aspects that had been discussed in a classification of phase transitions based on singularity theory. Finally, we discuss ergodicity breaking, which is highlighted by the presence of gaps in the accessible values of magnetization at low energies: it also displays new interesting patterns that are not present in the Blume-Capel model. Comment: Small additions in the Conclusions |
| Databáze: | OpenAIRE |
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