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 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.
Highlights
Quasiparticle - a key concept to describe interacting particles - characterizes electronelectron interaction in metals (Fermi liquid) and electron pairing in superconductors
We explain the basic concept of Bayesian analysis by showing its application to an energy distribution curve (EDC) contributed by multiple bands
Many solutions for peak position and peak width are plotted in the parameter space and colored with the posterior probability density proportional to the Boltzmann factor, where the point with the highest posterior probability density corresponds to the best-fit parameters as highlighted in Fig. 1c [note that “marginal” posterior probability density is plotted in Fig. 1c, because the intensity of each peak is a model parameter]
Summary
Quasiparticle - a key concept to describe interacting particles - characterizes electronelectron interaction in metals (Fermi liquid) and electron pairing in superconductors. Angle-resolved photoemission spectroscopy (ARPES) has played a pivotal role in uncovering key quasiparticle properties by capturing the energy dispersion (E–k relation) and lifetime of, e.g., Bogoliubov quasiparticles associated with the superconducting Cooper pairing in high-temperature superconductors[1,2,3] and mass-renormalized quasiparticles caused by strong electron–phonon coupling on metal surfaces and quasi-two-dimensional (quasi-2D) materials[4,5,6] As highlighted by these examples, for the understanding of the origin and mechanism of exotic physical properties of novel materials, it is crucial to experimentally establish the nature of quasiparticles. 7,8), or it was empirically approximated with a polynomial function (e.g., linear or parabola[9,10]) While such data analysis certainly gave insights into the quasiparticle dynamics, one often faced a serious problem in clarifying the nature of many-body interactions. These controversies partially originate from a few assumptions one had to make to extract Ek and Σ
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