Nutation dynamics and multifrequency resonance in a many-body seesaw

TL;DR

This paper explores multifrequency resonance phenomena in a many-body tilted Bose-Hubbard model, revealing conditions for wave function revival, effective two-level dynamics, and phase diagram characteristics, extending single-particle resonance physics to complex many-body systems.

Contribution

It generalizes multifrequency resonance physics from single-particle models to a many-body system, analyzing wave function revival, phase diagrams, and effective two-level dynamics in the tilted Bose-Hubbard model.

Findings

Wave function recovers at specific commensurate frequencies.

Dynamics reduces to spin precession and nutation around an oscillating axis.

Low-frequency regime leads to thermalization, strong modulation yields Floquet Hamiltonian behavior.

Abstract

The multifrequency resonance has been widely explored in some of the single-particle models, in which the modulating Rabi model has been most widely investigated. It has been found that with the diagonal periodic modulation, a steady dynamics can be realized in some well-defined discrete frequencies. These frequencies are independent of the off-diagonal couplings. In this work, we generalize this physics to the many-body seesaw realized using the tilted Bose-Hubbard model. We find that the wave function will recover to its initial condition when the modulation frequency is commensurate with the initial energy level spacing between the ground and the first excited levels. The period is determined by the driving frequency and commensurate ratio. In this case, the wave function will almost be restricted to the lowest two instantaneous energy levels. By projecting the wave function to these two relevant states, the dynamics is exactly the same as that for the spin precession dynamics and nutation dynamics around an oscillating axis. We map out the corresponding phase diagram and show that in the low-frequency regime the state is thermalized and in the strong modulation limit, the dynamics is determined by the effective Floquet Hamiltonian. The measurement of these dynamics from the mean position and mean momentum in phase space are also discussed. Our results provide a new thought about the multifrequency resonance in the many-body system.