A cascade of delocalization transitions and many-body localization in the interpolating Aubry-André-Fibonacci model

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• Antonio Strkalj, University of Cambridge
• Thursday 03 March 2022, 13:15-14:30
• Theory Library.

If you have a question about this talk, please contact Dr Hannah Price.

Model Hamiltonians with quasiperiodic order display a hierarchy of phenomena at different scales and are excellent starting points to explore unconventional effects not achievable in periodic solids. In this talk, I will present a theoretical study of localization in a one-dimensional interpolating Aubry-André-Fibonacci (IAAF) model. This model continuously interpolates between two well-known quasiperiodic examples: the Aubry-André model, known for a metal-to-insulator transition at finite potential strength, and the Fibonacci model, which is always critical. In a single-particle case, contrary to what one would naively expect, we find that the IAAF model has a non-monotonous and non-uniform behaviour of the spectrum. More precisely, we discover that by controllably evolving an Aubry-André into a Fibonacci model, a series of localization-delocalization transitions take place before the spectrum becomes critical. In a many-body IAAF model, we find that interactions between particles extend the ergodic phase in the Aubry-André limit, whereas they shrink it in the Fibonacci limit. The cascade of localization transitions found in the single-particle case is destroyed even for weak interactions. Moreover, in the region of the parameter space where the single-particle spectrum contains a non-trivial mobility edge, an anomalous effect is observed with tuning the many-body interactions, namely, weak interactions localize the system, whereas stronger interactions enhance ergodicity.

This talk is part of the Theoretical Physics Seminars series.

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