Unveiling quasiparticle dynamics of topological insulators through Bayesian modelling

TL;DR

This paper introduces a Bayesian modelling approach to disentangle many-body effects from experimental quasiparticle spectra, successfully revealing intrinsic properties of topological insulators and advancing understanding of quasiparticle dynamics in quantum materials.

Contribution

It presents a novel Bayesian inverse problem framework to analyze quasiparticle spectra, enabling extraction of intrinsic energy gaps and lifetimes in topological insulators.

Findings

Successfully extracted intrinsic energy gap of Dirac quasiparticles.

Revealed unusual quasiparticle lifetime behavior.

Demonstrated broad applicability to quantum materials.

Abstract

Quasiparticle - a key concept to describe interacting particles - characterizes electron-electron interaction in metals (Fermi liquid) and electron pairing in superconductors. While this concept essentially relies on the simplification of hard-to-solve many-body problem into one-particle picture and residual effects, a difficulty in disentangling many-body effects from experimental quasiparticle signature sometimes hinders unveiling intrinsic low-energy dynamics, as highlighted by the fierce controversy on the origin of Dirac-band anomaly in graphene and dispersion kink in high-temperature superconductors. Here, we propose an approach to solve this fundamental problem - the Bayesian modelling of quasiparticles. We have chosen a topological insulator $\mathrm{TlBi(S,Se)_2}$ as a model system to formulate an inverse problem of quasiparticle spectra with semiparametric Bayesian analysis, and successfully extracted one-particle and many-body characteristics, i.e. the intrinsic energy gap and unusual lifetime in Dirac-quasiparticle bands. Our approach is widely applicable to clarify the quasiparticle dynamics of quantum materials.