Immersing a mobile impurity particle in a quantum many-body environment can reveal

fundamental features of the background medium. This is particularly intriguing when

considering media with exotic properties such as strongly-correlated topological states of matter. Collaborating with other theorists from Univ. of Bruxelles and Harvard, Georg Bruun has recently demonstrated that a mobile impurity particle interacting with other particles residing in the edge modes of topological quantum matter acquires several characteristic properties such as an asymmetric energy dispersion with a band gap opening, when the velocity of the particle approaches that of the topological edge particles. This is shown analytically for low energy effective models as well as by adapting advanced tensor-network methods for strongly correlated fractional Chern insulators. The results demonstrate that injecting mobile impurity particles is a powerful way to probe exotic edge properties of topological quantum matter, particularly suitable for cold atom experiments.

The paper can be found here: https://www.nature.com/articles/s41467-025-60166-w