Reentrant Localization in Quasiperiodic Thue-Morse Chain

Abstract: We investigate localization and reentrance in a dimerized Su-Schrieffer-Heeger (SSH) tight-binding chain whose on-site energies are given by a quasiperiodic cosine masked by a deterministic Thue-Morse sequence. Working with non-interacting, spinless fermions, we solve the model via exact diagonalization on large Fibonacci sizes and diagnose phases using inverse/normalized participation ratios and the correlation fractal dimension. We identify boundaries separating extended, multifractal (mixed), and localized regimes by constructing a phase diagram in the plane of modulation strength and dimerization ratio. As the quasiperiodic amplitude is increased, the system exhibits reentrant behavior, localizing, partially re-delocalizing into a multifractal regime, and re-localizing, verified via two-size crossings of band-averaged observables and finite-size scaling. We demonstrate that tuning the modulation strength, the SSH dimerization, or the incommensurability parameter provides control over the critical thresholds. Our results suggest a versatile, randomness-free platform for the deterministic control of transport, enabling switching between conducting, multifractal, and insulating states.