Localization in disordered systems with interactions

Léa Ferreira dos Santos, Francisco Pérez-Bernal, Fausto Brogonovi +1 more

Rajeev Singh, Efrat Shimshoni

Localization in interacting systems caused by disorder, known as many‐body localization (MBL), has attracted a lot of attention in recent years. Most systems studied in this context also show single‐particle localization, and the question of MBL is whether the phenomena survives the effects of interactions. It is intriguing to consider a system with no single‐particle localization but which does localize in the presence of many particles. The localization phenomena occurs “due to” rather than “in spite of” interactions in such systems. We consider a simple bosonic system and show that interactions enhance the effects of very weak disorder and result in localization when many particles are present. We provide physical insights into the mechanism involved and support our results with analytical and numerical calculations. image

Marcel Goihl, Christian Krumnow, Marek Gluza +2 more

Spin chains with a symmetry-protected edge zero modes can be seen as prototypical systems for exploring topological signatures in quantum systems. However in an experimental realization of such a system, spurious interactions may cause the edge zero modes to delocalize. To combat this influence beyond simply increasing the bulk gap, it has been proposed to harness disorder which does not drive the system out of a topological phase. Equipped with numerical tools for constructing locally conserved operators that we introduce, we comprehensively explore the interplay of local interactions and disorder on localized edge modes in such systems. Contrary to established heuristic reasoning, we find that disorder has no effect on the edge mode localization length in the non-interacting regime. Moreover, disorder helps localize only a subset of edge modes in the truly interacting regime. We identify one edge mode operator that behaves as if subjected to a non-interacting perturbation, i.e., shows no disorder dependence. This implies that in finite systems, edge mode operators effectively delocalize at distinct interaction strengths despite the presence of disorder. In essence, our findings suggest that the ability to identify and control the best localized edge mode trumps any gains from introducing disorder.

Rheinischen Friedrich-Wilhelms-Universität

Mogus Degoyae Mochena

Adrian Braemer, Titus Franz, Matthias Weidemüller +1 more

Strongly interacting quantum systems subject to quenched disorder exhibit intriguing phenomena such as glassiness and many-body localization. Theoretical studies have mainly focused on disorder in the form of random potentials, while many experimental realizations naturally feature disorder in the interparticle interactions. Inspired by cold Rydberg gases, where such disorder can be engineered using the dipole blockade effect, we study a Heisenberg XXZ spin model where the disorder is exclusively due to random spin-spin couplings, arising from power-law interactions between randomly positioned spins. Using established spectral and eigenstate properties and entanglement entropy, we show that this system exhibits a localization crossover and identify strongly interacting pairs as emergent local conserved quantities in the system, leading to an intuitive physical picture consistent with our numerical results.