Starting from a deformed potential we construct separate bases of collective neutron and proton rotational states by exact angular momentum projection. These rotational states are then coupled by diagonalizing a residual pairing plus quadrupole interaction. Many new bands emerge that are not found in the rotation of the usual BCS condensate, and may correspond to the geometrical scissors mode and its generalizations. These excitation modes can be understood as rotational bands built on spin- $1\ensuremath{\Elzxh}$ phonon excitations; they exhibit a nearly perfect dynamical $\mathrm{SU}(3)$ fermion spectrum, even though there is no explicit dynamical symmetry in our model.Starting from a deformed potential we construct separate bases of collective neutron and proton rotational states by exact angular momentum projection. These rotational states are then coupled by diagonalizing a residual pairing plus quadrupole interaction. Many new bands emerge that are not found in the rotation of the usual BCS condensate, and may correspond to the geometrical scissors mode and its generalizations. These excitation modes can be understood as rotational bands built on spin- $1\ensuremath{\Elzxh}$ phonon excitations; they exhibit a nearly perfect dynamical $\mathrm{SU}(3)$ fermion spectrum, even though there is no explicit dynamical symmetry in our model.

Physical Review LettersJan 26, 199824 citations

Particle-Hole Excitations and the BCS Ground State

J. D. Fan, YURIY M. MALOZOVSKY

Bulletin of the American Physical SocietyMar 21, 20050 citations

Collective excitations and ground state correlations

E. Heinz, H. Müther, Harry A. Mavromatis

arXiv:nucl-th/9408020Nuclear Physics AMay 1, 19957 citations

Collective modes and the effect of single-particle excitations in the BCS-BEC crossover region of a trapped Fermi superfluid

Yoji Ohashi, Allan Griffin

We investigate the collective oscillations in the BCS-BEC crossover region of a trapped Fermi superfluid at T=0. We explicitly include the effect of a Feshbach resonance, which leads to a tunable pairing interaction adjusted by the threshold energy of the resonance, as well as the associated mol ecules. In a previous paper,we obtained solutions of the Bogoliubov-de Gennes coupled equations, describing a trapped Fermi superfluid ga s. Using these Bogoliubov quasi-particle excitations, we calculate the density correlation function in the Hartree-Fock-Bogoliubov generalized random phase approximation (HFB-GRPA). Previous discussions of collective modes were based on solving the T=0 equation of motion for the superfluid in a trap, ignoring the effect of single-particle excitations. We determine the frequencies of the quadrupole and the monopole modes. In the crossover region, the frequencies of these two modes are shown to be stro ngly depressed by the threshold energy of the two-particle continuum, originating from Andreev single-particle bound states (or in-gap states) localized at the edge of the trap. This effect becomes less important as one enters the BEC regime, due to the absence of these low energy fermion bound states. This suppression of collective mode frequencies by the two-particle continuum may be a useful experimental signature of the single-particle energy gap in the crossover region of trapped Fermi superfluids.We investigate the collective oscillations in the BCS-BEC crossover region of a trapped Fermi superfluid at T=0. We explicitly include the effect of a Feshbach resonance, which leads to a tunable pairing interaction adjusted by the threshold energy of the resonance, as well as the associated mol ecules. In a previous paper,we obtained solutions of the Bogoliubov-de Gennes coupled equations, describing a trapped Fermi superfluid ga s. Using these Bogoliubov quasi-particle excitations, we calculate the density correlation function in the Hartree-Fock-Bogoliubov generalized random phase approximation (HFB-GRPA). Previous discussions of collective modes were based on solving the T=0 equation of motion for the superfluid in a trap, ignoring the effect of single-particle excitations. We determine the frequencies of the quadrupole and the monopole modes. In the crossover region, the frequencies of these two modes are shown to be stro ngly depressed by the threshold energy of the two-particle continuum, originating from Andreev single-particle bound states (or in-gap states) localized at the edge of the trap. This effect becomes less important as one enters the BEC regime, due to the absence of these low energy fermion bound states. This suppression of collective mode frequencies by the two-particle continuum may be a useful experimental signature of the single-particle energy gap in the crossover region of trapped Fermi superfluids.

arXiv:cond-mat/0503641Mar 28, 20050 citations

Quartet Structures of Particles and Quasiparticles in the BCS Model

J. D. Fan, Y. M. Malozovsky

Journal of Superconductivity and Novel MagnetismFeb 8, 20105 citations

\mathrm{SU}(3)

fermion spectrum, even though there is no explicit dynamical symmetry in our model.