Symmetry-protected topological polarons

TL;DR

This paper uncovers the topological properties of polarons, a type of quasiparticle, by establishing symmetry principles, classifying their textures, and proposing experimental detection methods.

Contribution

It introduces a universal group-theoretic framework to classify topological polar textures in polarons and validates this with first-principles calculations.

Findings

Identified four classes of topological polar textures in polarons.

Demonstrated that these textures carry integer topological charges.

Proposed experimental methods to detect topological polarons.

Abstract

Emergent quasiparticles in solids often exhibit unique topological properties as a result of the complex interplay between charge, orbital, spin and lattice degrees of freedom. Among these quasiparticles, the polaron occupies a special place as the first known manifestation of the interaction between a fermion and a boson field. While polarons have been investigated for almost a century, whether these quasiparticles exhibit topological properties and why remain open questions. Here, we establish the universal symmetry principles governing the topology of polar textures in large polarons. Using a group-theoretic analysis, we identify four distinct classes of polar textures in time-reversal-invariant systems, and we show that they carry integer topological charges. We validate this classfication by performing state-of-the-art first-principles calculations of materials representative of each class. For these materials, we compute the fingerprints of polaron topology in Huang diffuse scattering, and propose ultrafast electron and X-ray scattering experiments to detect these quasiparticles.