Ultracold atoms in a bichromatic optical lattice provide an ideal platform to study disorder-induced localization phenomena. The system is conveniently described by the Aubry-André (AA) model, which allows us to make strong connections between theory and experiments. Further, using an ultracold atom platform allows us to easily introduce dynamic modulation; we have performed a series of experiments, where modulation is utilized to probe, alter and control the disordered system implemented by the bichromatic lattice. In the first experiment, we periodically kick the secondary disorder lattice, which implements the kicked AA model [1]. When the kick period is comparable or longer than the tunneling time of the underlying lattice, the system is theoretically expected to exhibit a rich phase structure as a function of the kick period and the disorder strength. In the experiment, we indeed observe the intricate phase structure and observe anomalous reentrant localization. In the second experiment, we phase-modulate the secondary disorder lattice, which effectively changes the disorder strength and allows us to reversibly control the localization [2]. In our most recent experiment, we phase-modulate the primary and secondary lattice at the same time [3]. This allows us to study the interplay between the modulation-induced localization (dynamic localization) and disorder-induced localization. We map out the rich phase diagram in the space of the driving strength and disorder strength and observe several features, which can be attributed to higher-order terms beyond the high-frequency-drive approximation.
References:
[1] T. Shimasaki et al., Nature Physics 20, 409 (2024).
[2] T. Shimasaki et al., arXiv:2312.00976, to appear in PRL.
[3] P. Dotti et al., arXiv:2406.00214.
Host: Charles Brown