Research news

Graph theory and tunable slow dynamics in quantum East Hamiltonians

In our recent study Menzler et al., Phys. Rev. B 112, 115141 (2025) we show how graph theory concepts can provide insight into the origin of slow dynamics in systems with kinetic constraints. In particular, we observe that slow dynamics is related to the presence of strong hierarchies between nodes on the Fock-space graph in the particle occupation basis, which encodes configurations connected by a given Hamiltonian. To quantify hierarchical structures, we generalize a centrality measure from graph theory to Hamiltonians. For the paradigmatic quantum East model, we show numerically that a connection between non-ergodic dynamics and these generalized graph measures can be established.

Interaction-induced Thouless pumping

In a joint theory-experiment collaboration between the ETH Zurich, Centro Atomico Bariloche and our group published in Phys. Rev. X 14, 021049 (2024) , we demonstrate interaction induced charge pumping in a system of interacting fermions in a quantum gas experiment, supported by numerical simulations for realistic conditions. This constitutes one of the first instances of topology in an interacting system. The initial quantized pumping is eventually surpassed by a breakdown due low-energy spin excitations, rooted in the many-body physics of the ionic Hubbard model. The figure shows a sketch of the experimental set-up.

Delocalization in patterned disorder potentials

Understanding the emergent dynamics of many-body quantum systems in the presence of disorder remains a key topic in condensed matter theory. In our recent work Rev. B 109, 125127 (2024), we investigate the dynamics and entanglement in the presence of a patterned disorder, where clean sites are periodically immersed into a disordered system. We demonstrate that this leads to high-entanglement states in the sea of area law states on finite systems, and consequently, initial state dependent relaxation dynamics. The figure shows the set-up and relevant initial states.