Café com Física



04 de outubro de 2017
Sala 18 (Cristalografia)

Mônica Caracanhas

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

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)∝ ln^2T. 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)∝ T^ν with an interaction-dependent exponent ν. The different regimes can be detected in the nonequilibrium expansion dynamics of an initially confined impurity.