title: Few-Body Precursor of the Higgs Mode in a Fermi Gas.
abstract: We demonstrate that an undamped few-body precursor of the Higgs mode can be investigated in a harmonically trapped Fermi gas. Using exact diagonalization, the lowest monopole mode frequency is shown to depend nonmonotonically on the interaction strength, having a minimum in a crossover region. The minimum deepens with increasing particle number, reflecting that the mode is the few-body analogue of a many-body Higgs mode in the superfluid phase, which has a vanishing frequency at the quantum phase transition point to the normal phase. We show that this mode mainly consists of coherent excitations of time-reversed pairs, and that it can be selectively excited by modulating the interaction strength, using, for instance, a Feshbach resonance in cold atomic gases.
authors.affiliation: Mathematical Physics, LTH, Lund University, SE-22100 Lund, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Bjerlin
authors.affiliation: Mathematical Physics, LTH, Lund University, SE-22100 Lund, Sweden.
authors.forename: S M
authors.initials: SM
authors.lastname: Reimann
authors.affiliation: Department of Physics and Astronomy, University of Aarhus, Ny Munkegade, DK-8000 Aarhus C, Denmark.
authors.forename: G M
authors.initials: GM
authors.lastname: Bruun