Fluctuation Spectra and Response Function of Coupled Atomic and Molecular BECs

Abstract

We investigate out-of-equilibrium properties of atomic molecular Bose Einstein condensates coupled through a Feshbach resonance, with the Feshbach coupling and detuning subject to Gaussian white noise. Using a bosonic Josephson junction framework and a Bloch sphere description, we examine the interplay of detuning, coherence, and noise governing the system dynamics. Coupling and detuning noise produce distinct fluctuation spectra, featuring both Feshbach resonant and symmetric off resonant peaks. We characterize the dispersive and absorptive response of the atom dimer system under periodic driving. The atom molecule hybridization at the Feshbach resonance maximizes the linewidth and minimizes both the effective temperature and the phase difference between the driving field and the system. This leads to an optimized power utilization and quality factor.