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.

准粒子——描述相互作用粒子的一个关键概念——表征金属（费米液体）中的电子-电子相互作用和超导体中的电子配对。虽然这个概念本质上依赖于将难以解决的多体问题简化为单粒子图像和残余效应，但从实验准粒子特征中解开多体效应的困难有时会阻碍揭示内在的低能量动力学，正如所强调的由关于石墨烯中狄拉克带异常和高温超导体中的色散扭结起源的激烈争论。在这里，我们提出了一种解决这个基本问题的方法——准粒子的贝叶斯建模。我们选择了拓扑绝缘体 TlBi(S,Se) ₂作为一个模型系统，用半参数贝叶斯分析来制定准粒子谱的逆问题，并成功地提取出单粒子和多体特征，即狄拉克准粒子带中的固有能隙和异常寿命。我们的方法广泛适用于阐明量子材料的准粒子动力学。