We measure excitation spectra of an ultracold gas of fermionic (40)K atoms in the BCS-Bose-Einstein-condensation (BEC) crossover regime. The measurements are performed with a novel spectroscopy that employs a small modulation of the B field close to a Feshbach resonance to give rise to a modulation of the interaction strength. With this method we observe both a collective excitation as well as the dissociation of fermionic atom pairs in the strongly interacting regime. The excitation spectra reveal the binding energy or excitation gap for pairs in the crossover region.We measure excitation spectra of an ultracold gas of fermionic (40)K atoms in the BCS-Bose-Einstein-condensation (BEC) crossover regime. The measurements are performed with a novel spectroscopy that employs a small modulation of the B field close to a Feshbach resonance to give rise to a modulation of the interaction strength. With this method we observe both a collective excitation as well as the dissociation of fermionic atom pairs in the strongly interacting regime. The excitation spectra reveal the binding energy or excitation gap for pairs in the crossover region.

arXiv:cond-mat/0407381Physical Review LettersFeb 24, 2005162 citations

Low-Energy Excitations in a Fermionic Superfluid

Andreas Schmitt

Lecture notes in physicsJun 13, 20140 citations

A Fermion-like description of condensed Bosons in a trap

Ranjan Bhaduri, M. V. N. Murthy

A Bose-Einstein condensate of atoms, trapped in an axially symmetric harmonic potential, is considered. By averaging the spatial density along the symmetry direction over a length that preserves the aspect ratio, the system may be mapped on to a zero temperature noninteracting Fermi-like gas. The ``mock fermions'' have a state occupancy factor $(>>1)$ proportional to the ratio of the coherance length to the ``hard-core'' radius of the atom. The mapping reproduces the ground state properties of the condensate, and is used to estimate the vortex excitation energy analytically. The ``mock-fermion'' description predicts some novel collective excitation in the condensed phase.A Bose-Einstein condensate of atoms, trapped in an axially symmetric harmonic potential, is considered. By averaging the spatial density along the symmetry direction over a length that preserves the aspect ratio, the system may be mapped on to a zero temperature noninteracting Fermi-like gas. The ``mock fermions'' have a state occupancy factor $(>>1)$ proportional to the ratio of the coherance length to the ``hard-core'' radius of the atom. The mapping reproduces the ground state properties of the condensate, and is used to estimate the vortex excitation energy analytically. The ``mock-fermion'' description predicts some novel collective excitation in the condensed phase.

arXiv:cond-mat/9606131Jun 18, 19960 citations

Solitons and vortices in ultracold fermionic gases

Tomasz Karpiuk, Mirosław Brewczyk, Kazimierz Rza̧żewski

We investigate the possibilities for the generation of solitons and vortices in a degenerate gas of neutral fermionic atoms. In analogy with the already experimentally demonstrated technique applied to a gaseous Bose-Einstein condensate we propose the phase engineering of a Fermi gas as a practical route to excited states with solitons and vortices. We stress that solitons and vortices appear even in a non-interacting fermionic gas. For solitons, in a system with a sufficiently large number of fermions and appropriate trap configuration, the Pauli blocking acts as the interaction between particles.We investigate the possibilities for the generation of solitons and vortices in a degenerate gas of neutral fermionic atoms. In analogy with the already experimentally demonstrated technique applied to a gaseous Bose-Einstein condensate we propose the phase engineering of a Fermi gas as a practical route to excited states with solitons and vortices. We stress that solitons and vortices appear even in a non-interacting fermionic gas. For solitons, in a system with a sufficiently large number of fermions and appropriate trap configuration, the Pauli blocking acts as the interaction between particles.

arXiv:cond-mat/0103564Journal of Physics B Atomic Molecular and Optical PhysicsJul 3, 200218 citations

Fermion Condensation in Strongly Interacting Fermi Liquids

Elena V. Kirichenko, V. A. Stephanovich

Nov 26, 20170 citations

(>>1)

proportional to the ratio of the coherance length to the ``hard-core'' radius of the atom. The mapping reproduces the ground state properties of the condensate, and is used to estimate the vortex excitation energy analytically. The ``mock-fermion'' description predicts some novel collective excitation in the condensed phase.