Topological polarons in halide perovskites

TL;DR

This paper reveals that halide perovskites host a diverse range of topologically nontrivial polarons, which may explain their exceptional optoelectronic properties and provide new insights into electron-phonon interactions.

Contribution

It introduces the discovery of topologically nontrivial polarons in halide perovskites through detailed first-principles simulations, a novel finding in this material class.

Findings

Identification of small and large polarons and charge density waves.

Support for topologically nontrivial phonon fields with quantized charge.

Explanation of experimental observations related to polaronic behavior.

Abstract

Halide perovskites emerged as a revolutionary family of high-quality semiconductors for solar energy harvesting and energy-efficient lighting. There is mounting evidence that the exceptional optoelectronic properties of these materials could stem from unconventional electron-phonon couplings, and it has been suggested that the formation of polarons and self-trapped excitons could be key to understanding such properties. By performing first-principles simulations with unprecedented detail across the length scales, here we show that halide perovskites harbor a uniquely rich variety of polaronic species, including small polarons, large polarons, and charge density waves, and we explain a variety of experimental observations. We find that these emergent quasiparticles support topologically nontrivial phonon fields with quantized topological charge, making them the first non-magnetic analog of the helical Bloch points found in magnetic skyrmion lattices.