Coherent control of localization in modulated quasiperiodic lattices

We report experiments demonstrating reversible coherent control of a localization phase transition by phasonic modulation. As background, we recently reported phasonic spectroscopy of a quantum gas in an artificial quasicrystal realized by a bichromatic optical lattice [1]. In that work, we studied how rapid phase modulation of the secondary optical lattice (phason modulation) causes atoms to absorb energy at high harmonics of the drive frequency. In this talk, we discuss phase modulation in a lower frequency regime where excitation into higher bands is not significant but the modulation frequency is high enough to avoid intraband excitations [2]. In particular, we investigated the phase modulation amplitude dependence of the localization properties of the quasicrystal. In this regime, the effect of the phase modulation is to renormalize the effective lattice depth of the phase modulated secondary lattice [1]. By monitoring transport in the modulated bichromatic lattice, we observed that the effective variation of the secondary lattice depth causes a number of localization-delocalization transitions as the phason drive amplitude is increased. These results open a new path to dynamical coherent control of the transport properties of quantum matter.

[1] S. Rajagopal et al., Phys. Rev. Lett. 123, 223201 (2019)

[2] G.Sun and A. Eckardt, Phys. Rev. Res. 2, 013241 (2020)