Abstract: Free energy as a function of polarization is calculated for the square-lattice J1-J2 Ising model for J2 < |J1|/2 using the random local field approximation (RLFA) and Monte Carlo (MC) simulations. Within RLFA, it reveals a metastable state with zero polarization in the ordered phase. In addition, the Landau free energy calculated within RLFA indicates a geometric slab-droplet phase transition at low temperature, which cannot be predicted by the mean field approximation. In turn, restricted free energy calculations for finite-size samples, exact and using MC simulations, reveal metastable states with a wide range of polarization values, but with only two domains. Taking into account the dependence of the restricted free energy on the nearest-neighbor correlations allows us to identify several more metastable states. The calculations also reveal additional slab-droplet transitions at J2 > |J1|/4. These findings enrich our knowledge of the J1-J2 Ising model and the RLFA as a useful theoretical tool to study phase transitions in spin systems.

Cite: Abalmasov V.A.
Free energy and metastable states in the square-lattice J1-J2 Ising model
SciPost Physics. 2024. V.16. N6. 151 :1-21. DOI: 10.21468/SciPostPhys.16.6.151 WOS Scopus РИНЦ OpenAlex

Dates:

Submitted:	Jan 11, 2024
Accepted:	May 28, 2024
Published print:	Jun 6, 2024
Published online:	Jun 6, 2024

Identifiers:

Web of science:	WOS:001244475200002
Scopus:	2-s2.0-85195849519
Elibrary:	68109533
OpenAlex:	W4399382315

Citing:

DB	Citing
Scopus	2
Web of science	2
OpenAlex	2

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