Início
Agenda 

 04 de outubro de 2017
16h30 Sala
18 (Cristalografia) 

Mônica
Caracanhas

IFSC


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 twodimensional Fermi
gas with quadratic band touching the polaron picture may either
hold or break down depending on the particlehole 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
onedimensional channels and use conformal field theory
techniques to obtain D(T)∝ T^ν with an interactiondependent
exponent ν. The different regimes can be detected in the
nonequilibrium expansion dynamics of an initially confined
impurity.



