Tunable breakdown of the polaron picture for mobile impurities in a topological semimetal

Article

关键词: DYNAMICS;    TRANSPORT;    MODEL;    SINGULARITY;    PARTICLE;    FERMIONS;    SPECTRA;   

DOI  :  10.1103/PhysRevB.94.220302

来源: SCIE

【 摘 要 】

Mobile impurities in cold atomic gases constitute a new platform for investigating polaron physics. Here we show that when impurity atoms interact with a two-dimensional Fermi gas with quadratic band touching, the polaron picture may either hold or break down depending on the particle-hole asymmetry of the band structure. If the hole band has a smaller effective mass than the particle band, the quasiparticle is stable and its diffusion coefficient varies with temperature as D(T)alpha ln(2) T. If the hole band has larger mass, the quasiparticle weight vanishes at low energies due to an emergent orthogonality catastrophe. In this case we map the problem onto a set of one-dimensional channels and use conformal field theory techniques to obtain D(T)alpha T-nu with an interaction-dependent exponent nu. The different regimes can be detected in the nonequilibrium expansion dynamics of an initially confined impurity.

【 授权许可】

Free