Multiscale Coupled Polarization and BKT Transitions in Tow-Dimensional Hybrid Organic-Inorganic Perovskites

TL;DR

This paper develops a two-dimensional XY rotor model to study polarization dynamics in layered hybrid perovskites, revealing the coexistence of ferroelectric order and topological BKT transitions, consistent with experimental observations.

Contribution

It introduces a comprehensive minimal model incorporating key interactions and anisotropies to explain complex phase behavior in layered hybrid perovskites.

Findings

Identification of low-temperature quasi-ferroelectric and high-temperature BKT regimes.

Reproduction of experimental dielectric susceptibility peaks.

Observation of vortex proliferation and domain wall scaling near transitions.

Abstract

We present an extended two-dimensional XY rotor model specifically designed to capture the polarization dynamics of hybrid organic-inorganic perovskite monolayers. This framework integrates nearest and next-nearest neighbor couplings, crystalline anisotropy inherent to perovskite lattice symmetries, external bias fields, and long-range dipolar interactions that are prominent in layered perovskite architectures. Through a combination of analytical coarse-graining and large-scale Monte Carlo simulations on 64*64 lattices, we identify two distinct thermodynamic regimes: a low-temperature quasi-ferroelectric state characterized by finite polarization and domain wall formation, and a higher-temperature Berezinskii-Kosterlitz-Thouless (BKT) crossover associated with vortex-antivortex unbinding and the suppression of long-range order. Our results reproduce key experimental signatures observed in quasi-two-dimensional perovskites, including dual peaks in dielectric susceptibility, enhanced vortex density near the transition, multistable polarization hysteresis under applied fields, and the scaling behavior of domain wall widths. This minimal yet realistic model provides a unifying perspective on how topological transitions and ferroelectric ordering coexist in layered perovskite systems, offering quantitative guidance for interpreting the emergent polar vortex lattices and complex phase behavior recently reported in hybrid perovskite thin films.