Low energy damping of collective modes in spinor Bose-Fermi mixtures

Yoji Asano

Chuanzhou Zhu, Li Chen, Hui Hu +2 more

Yoji Asano, Masato Narushima, Shohei Watabe +1 more

J. H. Pixley, Xiaopeng Li, S. Das Sarma

Using an effective field theory we describe the low energy bosonic excitations in a three-dimensional ultracold mixture of spin-1 bosons and spin-1/2 fermions. We establish an interesting fermionic excitation induced generic damping of the usual undamped long-wavelength bosonic collective Goldstone modes. Two states with bosons forming either a ferromagnetic or polar superfluid are studied. The linear dispersion of the bosonic Bogoliubov excitations is preserved with a renormalized sound velocity. For the polar superfluid we find both gapless modes (density and spin) are damped, whereas in the ferromagnetic superfluid we find the density (spin) mode is (not) damped. We find that this holds for any mixture of bosons and fermions that are coupled through at least a density-density interaction. In addition, we predict the existence of the Kohn anomaly in the bosonic excitation spectrum of Bose-Fermi mixtures. We discuss the implications of our many-body interaction results for experiments on Bose-Fermi mixtures.

Carsten Robens, Yiqi Ni, Zoe Z. Yan +2 more

Huitao Shen, Wei Zheng

We study Landau damping in a Bose-Fermi superfluid mixture at finite temperatures. We find that at low temperatures, the Landau damping rate will be exponentially suppressed on both the BCS side and the BEC side of the Fermi superfluid. The momentum dependence of the damping rate is obtained, and it is quite different from the BCS side to the BEC side since the dominated low-energy excitations are different on the two sides. The relation between our result and the collective mode experiment in the recently realized Bose-Fermi superfluid mixture is also discussed.