Decay of Polarons and Molecules in a Strongly Polarized Fermi Gas

Bruun, Georg M.; Massignan, Pietro

doi:10.1103/physrevlett.105.020403

Cited by 67 publications

(94 citation statements)

References 26 publications

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“…Apparent crossings found in 3D [14][15][16][17][18] and 2D [19,20] have been interpreted as sharp transitions between a "polaron" state |P and a "molecule" state |M . Sharp transitions of this type should not occur.…”

Section: The Exact Wave-function For One Reversed Spinmentioning

confidence: 99%

“…For K = 0 they take the form of Hartree-Fock equations for a system of particles of mass m/2 moving in a short-range potential gδ(x) with interactions (p i · p j )/m, where p i is the momentum of particle i. Equations analogous to (17) have been obtained for the Hubbard case [5,9] and it is not difficult to show that in the low density limit they reduce to (17) with 2 /2m = a 2 t, g = U a d as expected. We now wish to consider qualitatively the cross-over from the "polaron" to "molecule" regime from the present viewpoint.…”

Section: An Alternative Ansatzmentioning

confidence: 99%

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A smooth polaron–molecule crossover in a Fermi system

Edwards¹

2013

J. Phys.: Condens. Matter

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The problem of a single down spin particle interacting with a Fermi sea of up spin particles is of current interest in the field of cold atoms. The Hubbard model, appropriate to atoms in an optical lattice potential, is considered in parallel with a gas model. As the strength of an attractive shortrange interaction is increased there is a crossover from "polaron" behaviour, in which the Fermi sea is weakly perturbed, to "molecule" behaviour in which the down spin particle is bound to a single up spin particle. It is shown that this is a smooth crossover, not a sharp transition as claimed by many authors.

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Section: The Exact Wave-function For One Reversed Spinmentioning

confidence: 99%

Section: An Alternative Ansatzmentioning

confidence: 99%

A smooth polaron–molecule crossover in a Fermi system

Edwards¹

2013

J. Phys.: Condens. Matter

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“…The first branch, emerging from the N -fermion plus impurity state, was intensively studied in the case of zero-range single-channel models and is called the polaronic branch [8-11, 30, 31]. The second branch, emerging from the N −1-fermion plus closedchannel-molecule state, also exists in single-channel models [10,12,30]. It was studied in a two-channel model in [32,33] but only in the limit of a very broad and zerorange Feshbach resonance, where it becomes equivalent to the zero-range single-channel case already considered in [10,12,30].…”

Section: Polaronic and Dimeronic Variational Ansatzmentioning

confidence: 99%

Impurity in a Fermi sea on a narrow Feshbach resonance: A variational study of the polaronic and dimeronic branches

Trefzger

Castin

2012

Phys. Rev. A

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We study the problem of a single impurity of mass M immersed in a Fermi sea of particles of mass m. The impurity and the fermions interact through a s-wave narrow Feshbach resonance, so that the Feshbach length R * naturally appears in the system. We use simple variational ansatz, limited to at most one pair of particle-hole excitations of the Fermi sea and we determine for the polaronic and dimeronic branches the phase diagram between absolute ground state, local minimum, thermodynamically unstable regions (with negative effective mass), and regions of complex energies (with negative imaginary part). We also determine the closed channel population which is experimentally accessible. Finally we identify a non-trivial weakly attractive limit where analytical results can be obtained, in particular for the crossing point between the polaronic and dimeronic energy branches.

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“…The energy of a p = 0 molecule in the deep BEC limit 1/k F a 1 is with m 3 and a 3 the atom-dimer (↑ − ↑↓) reduced mass and scattering length [23]. To describe the decay into the molecule-hole continuum, it is necessary to go beyond the ladder approximation and include more particle-hole excitations [24]. Including such processes moves the threshold of the molecule-hole continuum, visible in Fig.…”

Section: Formalismmentioning

confidence: 99%

Repulsive polarons and itinerant ferromagnetism in strongly polarized Fermi gases

2011

Self Cite

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We analyze the properties of a single impurity immersed in a Fermi sea. At positive energy and scattering lengths, we show that the system possesses a well-defined but metastable excitation, the repulsive polaron, and we calculate its energy, quasiparticle residue and effective mass. From a thermodynamic argument we obtain the number of particles in the dressing cloud, illustrating the repulsive character of the polaron. Identifying the important 2-and 3-body decay channels, we furthermore calculate the lifetime of the repulsive polaron. The stability conditions for the formation of fully spin polarized (ferromagnetic) domains are then examined for a binary mixture of atoms with a general mass ratio. Our results indicate that mass imbalance lowers the critical interaction strength for phase-separation, but that very short quasiparticle decay times will complicate the experimental observation of itinerant ferromagnetism. Finally, we present the spectral function of the impurity for various coupling strengths and momenta.

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Decay of Polarons and Molecules in a Strongly Polarized Fermi Gas

Cited by 67 publications

References 26 publications

A smooth polaron–molecule crossover in a Fermi system

A smooth polaron–molecule crossover in a Fermi system

Impurity in a Fermi sea on a narrow Feshbach resonance: A variational study of the polaronic and dimeronic branches

Repulsive polarons and itinerant ferromagnetism in strongly polarized Fermi gases

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