Physique statistique
The mechanisms of phase ordering and critical phenomena can be efficiently studied using model Hamiltonians which capture the fundamental properties of different materials. By examining these models, we can unravel the complex behavior of these systems, revealing the emergence of novel phases, excitations, and transitions.
Emergent tricriticality in magnetic metamaterials
Recent work has included the study of phase diagrams with tri-critical and multi-critical points [1]. The dumbbell model of spin ice maps closely onto the antiferromagnetic S=2 Blume-Capel model in which spins take values ± 2, ±
1, 0 with spin creation controlled by a chemical potential. This systems shows an exotic phase diagram in the three dimensional space of temperature, chemical potential and symmetry breaking field with a double winged structure of first order transitions partitioning five different phases as shown in the figure below. The fist order surfaces end along lines of critical points which meet in a complex set of tri-critical points. The work is put in the general context of symmetry sustaining and liquid-liquid phase transitions. We have most recently shown that in two-dimensional Blume-Capel models with continuous symmetry, the Kosterlitz-Thouless transition can evolve into a first order transition via a very particular kind of multi-critical points [2].
- V. Raban, C. Suen, L. Berthier, and P. Holdsworth, Physical Review B 99, 224425 (2019).
- Björn Erik Skovdal, Gunnar K. Pálsson, P. C. W. Holdsworth, and Björgvin Hjörvarsson, Phys. Rev. B 107, 184409 (2023).