BKT phase transition in a 2d system with long range dipole-dipole interaction

TL;DR

This paper demonstrates that a Berezinskii-Kosterlitz-Thouless (BKT) phase transition occurs in 2D XY-like systems with long-range dipole-dipole interactions, affecting vortex behavior and transition temperature.

Contribution

It shows that BKT transition always occurs in such systems, with unique vortex polarization and screening effects due to dipole interactions.

Findings

Bound vortex-antivortex pairs polarize and screen interactions

The phase transition occurs at a higher temperature than in systems without dipole interactions

Vortex pairs dissociate at the transition, leading to a disordered phase

Abstract

We consider phase transitions in 2d XY-like systems with long range dipole-dipole interactions and demonstrate that BKT-type phase transition always occurs separating the ordered (ferroelectric) and the disordered (paraelectric) phases. The low-temperature phase corresponds to a thermal state with bound vortex-antivortex pairs characterized by linear attraction at large distances. We show that bound vortex pairs polarize and screen the vortex-antivortex interaction leaving only the logarithmic attraction at sufficiently large separations between the vortices. At higher temperatures the pairs dissociate and the phase transition similar to BKT occurs, though at a larger temperature than in a system without the dipole-dipole interaction.