Non-linear response of interacting bosons in a quasiperiodic potential

TL;DR

This paper investigates how interacting bosons in a quasiperiodic potential respond to electric pulses, revealing how harmonic content in the current distinguishes localized and delocalized phases and how interactions modify this behavior.

Contribution

It provides a theoretical analysis of non-linear current response in interacting bosons within quasiperiodic potentials, highlighting harmonic signatures of different phases and the effects of interactions.

Findings

Delocalized phase exhibits only odd harmonics in current.

Localized phase shows both even and odd harmonics.

Interactions influence harmonic amplitudes and phase distinctions.

Abstract

We theoretically study the electric pulse-driven non-linear response of interacting bosons loaded in an optical lattice in the presence of an incommensurate superlattice potential. In the non-interacting limit $(U=0)$, the model admits both localized and delocalized phases depending on the strength of the incommensurate potential $V_0$. We show that the particle current contains only odd harmonics in the delocalized phase in contrast to the localised phase where both even and odd harmonics are identified. The relative magnitudes of these even and odd harmonics and sharpness of the peaks can be tuned by varying frequency and the number of cycles of the applied pulse, respectively. In the presence of repulsive interactions, the amplitudes of the even and odd harmonics further depend on the relative strengths of the interaction $U$ and the potential $V_0$. We illustrate that the disorder and interaction-induced phases can be distinguished and characterized through the particle current. Finally, we discuss the dynamics of field induced excitation responsible for exhibiting higher harmonics in the current spectrum.