We demonstrate that the quantum dynamics of a many-body Fermi-Bose system can be simulated using a Gaussian phase-space representation method. In particular, we consider the application of the mixed fermion-boson model to ultracold quantum gases and simulate the dynamics of dissociation of a Bose-Einstein condensate of bosonic dimers into pairs of fermionic atoms. We quantify deviations of atom-atom pair correlations from Wick's factorization scheme, and show that atom-molecule and molecule-molecule correlations grow with time, in clear departures from pairing mean-field theories. As a first-principles approach, the method provides benchmarking of approximate approaches and can be used to validate dynamical probes for characterizing strongly correlated phases of fermionic systems.We demonstrate that the quantum dynamics of a many-body Fermi-Bose system can be simulated using a Gaussian phase-space representation method. In particular, we consider the application of the mixed fermion-boson model to ultracold quantum gases and simulate the dynamics of dissociation of a Bose-Einstein condensate of bosonic dimers into pairs of fermionic atoms. We quantify deviations of atom-atom pair correlations from Wick's factorization scheme, and show that atom-molecule and molecule-molecule correlations grow with time, in clear departures from pairing mean-field theories. As a first-principles approach, the method provides benchmarking of approximate approaches and can be used to validate dynamical probes for characterizing strongly correlated phases of fermionic systems.

arXiv:0910.4440Europhysics Letters (EPL)Nov 1, 201010 citations

Quantum Phases of Atom-Molecule Mixtures of Fermionic Atoms

Nicolas Lopez, Shan-Wen Tsai, Eddy Timmermans +1 more

Bulletin of the American Physical SocietyMar 22, 20110 citations

Association and Dissociation of Ultracold Fermions Using an Oscillating Magnetic Field

Abhishek Mohapatra

The pairwise interactions of ultracold atoms can be resonantly enhanced by tuning the scattering length to infinity using a Feshbach resonance.In a gas of ultracold atoms whose scattering length is controlled by a magnetic Feshbach resonance, the atoms can be associated into universal dimers and the dimers can be dissociated into unbound atoms by using an oscillating longitudinal magnetic field with frequency near the binding energy of a dimer.If the gas of ultracold atoms are fermions, the oscillating magnetic field with frequency near the pairing gap can dissociate Cooper pairs into pairs of unbound atoms.In this thesis, we show that the transition rates for association and dissociation can be calculated by treating the oscillating magnetic field as a sinusoidal time-dependent perturbation proportional to the contact operator.We calculate both the harmonic and subharmonic transition rates analytically for association in a thermal gas of atoms and for dissociation in a thermal gas of dimers.We also calculate the harmonic transition rate analytically for the dissociation of Cooper pairs into pairs of unbound atoms in the BCS limit.Our results for the dissociation rate of Cooper pairs can be used to make a direct measurement of the pairing gap for fermionic atoms.The pairwise interactions of ultracold atoms can be resonantly enhanced by tuning the scattering length to infinity using a Feshbach resonance.In a gas of ultracold atoms whose scattering length is controlled by a magnetic Feshbach resonance, the atoms can be associated into universal dimers and the dimers can be dissociated into unbound atoms by using an oscillating longitudinal magnetic field with frequency near the binding energy of a dimer.If the gas of ultracold atoms are fermions, the oscillating magnetic field with frequency near the pairing gap can dissociate Cooper pairs into pairs of unbound atoms.In this thesis, we show that the transition rates for association and dissociation can be calculated by treating the oscillating magnetic field as a sinusoidal time-dependent perturbation proportional to the contact operator.We calculate both the harmonic and subharmonic transition rates analytically for association in a thermal gas of atoms and for dissociation in a thermal gas of dimers.We also calculate the harmonic transition rate analytically for the dissociation of Cooper pairs into pairs of unbound atoms in the BCS limit.Our results for the dissociation rate of Cooper pairs can be used to make a direct measurement of the pairing gap for fermionic atoms.

Jan 1, 20180 citations

Confinement versus deconfinement of Cooper pairs in one-dimensional spin- 3∕2 fermionic cold atoms

Sylvain Capponi, Guillaume Roux, P. Azaria +2 more

The phase diagram of spin- $3∕2$ fermionic cold atoms trapped in a one-dimensional optical lattice is investigated at quarter filling (one atom per site) by means of large-scale numerical simulations. In full agreement with a recent low-energy approach, we find two phases with confined and deconfined Cooper pairs separated by an Ising quantum phase transition. The leading instability in the confined phase is an atomic-density wave with subdominant quartet superfluid instability made of four fermions. Finally, we reveal the existence of a bond-ordered Mott insulating phase in some part of the repulsive regime.The phase diagram of spin-$3∕2$ fermionic cold atoms trapped in a one-dimensional optical lattice is investigated at quarter filling (one atom per site) by means of large-scale numerical simulations. In full agreement with a recent low-energy approach, we find two phases with confined and deconfined Cooper pairs separated by an Ising quantum phase transition. The leading instability in the confined phase is an atomic-density wave with subdominant quartet superfluid instability made of four fermions. Finally, we reveal the existence of a bond-ordered Mott insulating phase in some part of the repulsive regime.

arXiv:cond-mat/0612456Physical Review BMar 16, 200754 citations

Pairing of fermionic atoms in a strongly interacting quantum gas

Cheng Chin

APSMay 1, 20050 citations

The phase diagram of spin-

3∕2

fermionic cold atoms trapped in a one-dimensional optical lattice is investigated at quarter filling (one atom per site) by means of large-scale numerical simulations. In full agreement with a recent low-energy approach, we find two phases with confined and deconfined Cooper pairs separated by an Ising quantum phase transition. The leading instability in the confined phase is an atomic-density wave with subdominant quartet superfluid instability made of four fermions. Finally, we reveal the existence of a bond-ordered Mott insulating phase in some part of the repulsive regime.