Topological transport of mobile impurities

Abstract

We study the Hall response of topologically trivial mobile impurities (Fermi polarons) interacting weakly with majority fermions forming a Chern-insulator background. This setting involves a rich interplay between the genuine many-body character of the polaron problem and the topological nature of the surrounding cloud. When the majority fermions are accelerated by an external field, a transverse impurity current can be induced. To quantify this polaronic Hall effect, we compute the drag transconductivity, employing controlled diagrammatic perturbation theory in the impurity-fermion interaction. We show that the impurity Hall drag is not simply proportional to the Chern number characterizing the topological transport of the insulator on its own-it also depends continuously on particle-hole breaking terms, to which the Chern number is insensitive. However, when the insulator is tuned across a topological phase transition, a sharp jump of the impurity Hall drag results, for which we derive an analytical expression. We describe how to experimentally detect the polaronic Hall drag and its characteristic jump, setting the emphasis on the circular dichroism displayed by the impurity's absorption rate.

Lattice polaron in a Bose–Einstein condensate of hard-core bosons

“…The ability to probe lattice systems site-by-site using quantum microscopy has increased interest in the study of lattice polarons, which may serve as probes to measure quantum phase transitions [40], topological and geometric features [41][42][43][44], as well as following spatially non-equilibrium dynamics [51]. Entering into the strongly interacting regime may lead to the emergence of new few-body and many-body states [50].…”

“…In optical lattices, impurity physics has renewed interest in probing the Mott-insulator to superfluid transition [40], topological phases [41][42][43], band geometry [44], magnetic polarons [45][46][47][48][49], few-body physics [50], non-equilibrium dynamics [51], and polaron physics in strongly correlated Fermi-Hubbard models [52]. The study of lattice polarons is further motivated by the advances in quantum gas microscopy, which enables the imaging of individual atoms [53,54], providing intricate spatial details of quantum states that complement traditional spectroscopic information [45,55].…”

Collective excitations of a Bose–Einstein condensate of hard-core bosons and their mediated interactions: from two-body bound states to mediated superfluidity

“…Quantum microscopy delivered a powerful tool to explore phases of matter in optical lattices with site-by-site imaging [32], motivating the study of Bose lattice polarons [33], their mediated interactions [34] and strongly correlated physics with lattice Fermi polarons [35][36][37][38][39][40][41][42][43]. The increasing interest on strongly correlated quantum gases in optical lattices is therefore motivated by a parallel development of the abilities to measure such phases with unprecedented control.…”

Non-Hermitian Squeezed Polarons

“…In conventional Hermitian settings, polarons are many-body states dressed by the environment-impurity interaction, as observed in ultracold-atom experiments [92][93][94][95][96][97][98][99][100][101][102]. By providing an unique angle for understanding strong interactions in solid-state and cold-atom systems, they are valuable probes for detecting quantum phase transitions in interacting topological settings [103][104][105][106][107].…”