Formation and characterization of matter-wave soliton breathers

Solitons are non-dispersive wave packets which arise as solutions to the 1D nonlinear Schrodinger equation (NLSE). Due to the integrability of the NLSE, higher-order solitons, known as breathers, can be formed from fundamental solitons by a specific interaction quench. A n-soliton breather is composed of constituent solitons of mass ratios 1:3:...:2n-1, and is formed when the attractive interactions are quenched by a factor of n², where n is an integer. A breather’s density profile oscillates in time at a frequency determined by the chemical potential difference of its constituent solitons. While the relative velocity and positions of the solitons are conserved quantities in the mean-field (MF) limit, quantum manybody theory predicts that quantum fluctuations break integrability and lead to breather dissociation^1,2. In this work, we form solitons from a Bose-Einstein Condensate of ⁷Li atoms in a quasi-1D harmonic potential formed by a focused laser beam. Breathers are formed following an interaction quench controlled through the Feshbach resonance. We observe density profiles of 2- and 3-soliton breathers, and characterize their breathing frequencies with respect to atom number and confinement aspect ratio. Our findings agree well with a quasi-1D MF theory. We report the progress made towards observing breather dissociation.

1V. A. Yurovsky et al., PRL 119, 220401 (2017)

²O.V. Marchukov et. al, Phys. Rev. Lett. 125, 050405 (2020)