Bi-Critical Central Point Of J FN -J SN Ising Model Phase Diagram

TL;DR

This paper investigates the phase diagram of the J FN - J SN Ising model, revealing a bi-critical point where different ordered phases coexist and transition, with implications for understanding frustration and mixed structures.

Contribution

It introduces the concept of a bi-critical central point in the phase diagram of the J FN - J SN Ising model, highlighting the coexistence and transition of ordered phases.

Findings

Identification of ordered structures p(2X2) and degenerate p(2X1)/p(1X2) based on interaction ratios

Discovery of a bi-critical point where multiple phases coexist and transition occurs

Role of sum of densities as an order parameter in frustrated systems

Abstract

When interfaces between ordered domains are ordered clusters, frustration disappears. A phase with mixed ordered structures emerges but no length scale can be associated to. We show that sum of densities of each structure plays the role of order parameter. For, we consider a regular half full lattice with repulsive interaction extended to second neighboring particles. Ordered structures are p(2X2) when ratio between second and first neighboring interaction energies R=J SN /J FN <0.5 and degenerate p(2X1)/p(1X2) for R>0.5. The ground states coexist with another named p(4X2)/p(2X4) at central bi-critical point: a state to cross when passing between non-frustrated ordered phases.