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Sum Rule Approach to Collective Oscillations of Boson-Fermion Mixed Condensate of Alkali Atoms

T. Miyakawa·T. Suzuki·H. Yabu
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Abstract

The behavior of collective oscillations of a trapped boson-fermion mixed condensate is studied in the sum rule approach. Mixing angle of bosonic and fermionic multipole operators is introduced so that the mixing characters of the low-lying collective modes are studied as functions of the boson-fermion interaction strength. For an attractive boson-fermion interaction, the low-lying monopole mode becomes a coherent oscillation of bosons and fermions and shows a rapid decrease in the excitation energy towards the instability point of the ground state. In contrast, the low-lying quadrupole mode keeps a bosonic character over a wide range of the interaction strengths. For the dipole mode the boson-fermion in-phase oscillation remains to be the eigenmode under the external oscillator potential. For weak repulsive values of the boson-fermion interaction strengths we found that an average energy of the out-of-phase dipole mode stays lower than the in-phase oscillation. Physical origin of the behavior of the multipole modes against boson-fermion interaction strength is discussed in some detail.

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T. Miyakawa, T. Suzuki, H. Yabu. 2000-09-25. Sum Rule Approach to Collective Oscillations of Boson-Fermion Mixed Condensate of Alkali Atoms. https://doi.org/10.1103/physreva.62.063613

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