Thermal first-order phase transitions, Ising critical points, and reentrance in the Ising-Heisenberg model on the diamond-decorated square lattice in a magnetic field

RWTH Publications (RWTH Aachen)

Abstract

The thermal phase transitions of a spin-1/2 Ising-Heisenberg model on the diamond-decorated square lattice in a magnetic field are investigated using a decoration-iteration transformation and classical Monte Carlo simulations. A generalized decoration-iteration transformation maps this model exactly onto an effective classical Ising model on the square lattice with temperature-dependent effective nearest-neighbor interactions and magnetic field strength. The effective field vanishes along a ground-state phase boundary of the original model, separating a ferrimagnetic and a quantum monomer-dimer phase. At finite temperatures this phase boundary gives rise to an exactly solvable surface of discontinuous (first-order) phase transitions, which terminates in a line of Ising critical points. The existence of discontinuous reentrant phase transitions within a narrow parameter regime is reported and explained in terms of the low-energy excitations from both phases. These exact results, obtained from the mapping to the zero-field effective Ising model are corroborated by classical Monte Carlo simulations of the effective model.

Authors 6

1. Jozef Strečka

   University of Pavol Jozef Šafárik

   Affiliation as printed

   Department of Theoretical Physics and Astrophysics , Faculty of Science , P. J. Šafárik University , Park Angelinum 9 , 04001 Košice , Slovakia

2. Katarína Karľová

   University of Pavol Jozef Šafárik

   Affiliation as printed

   CY

   Department of Theoretical Physics and Astrophysics , Faculty of Science , P. J. Šafárik University , Park Angelinum 9 , 04001 Košice , Slovakia

3. Taras Verkholyak

   Yukhnovskii Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine

   Affiliation as printed

   Institute for Condensed Matter Physics , National Academy of Sciences of Ukraine , Svientsitskii Street 1 , 790 11 , L' viv , Ukraine

4. Nils Caci Aachen Institute for Theoretical Solid State Physics

   RWTH Aachen University · Jülich Aachen Research Alliance · CY Cergy Paris Université

   Affiliation as printed

   Cergy Paris Université , 95000 Cergy-Pontoise , France

   Institute for Theoretical Solid State Physics , JARA FIT, and JARA CSD , RWTH Aachen University , 52056 Aachen , Germany

5. Stefan Weßel Aachen Institute for Theoretical Solid State Physics

   RWTH Aachen University · Jülich Aachen Research Alliance

   Affiliation as printed

   Institute for Theoretical Solid State Physics , JARA FIT, and JARA CSD , RWTH Aachen University , 52056 Aachen , Germany

6. A. Honecker

   Centre National de la Recherche Scientifique · Laboratoire de Physique Théorique et Modélisation

   Affiliation as printed

   Laboratoire de Physique Théorique et Modélisation , CNRS UMR 8089 ,