Collective Excitations in Bose–Fermi Mixtures
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We investigate collective excitations of density fluctuations and a dynamic density structure factor in a mixture of Bose and Fermi gases in a normal phase. With decreasing temperature, we find that the frequency of the collective excitation deviates from that of the hydrodynamic sound mode. Even at a temperature much lower than the Fermi temperature, the collective mode frequency does not reach the collisionless limit analogous to zero sound in a Fermi gas, because of collisions between bosons and fermions.
KeywordsBose–Fermi mixture Collective excitation Normal state First sound Zero sound Dynamic structure factor
We are grateful to Y. Iijima for discussion in the early stage of this work. S.W. is supported by JSPS KAKENHI Grant Nos. (JP16K17774, JP18K03499), and T.N. is supported by JSPS KAKENHI Grant No. (JP16K05504).
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