Orateur
M.
Yvan Castin
(CNRS)
Description
The three-body Efimov effect leads, for a binary interaction of infinite s-wave scattering length and no dimer state, to an infinite number of trimer states, which is quite remarkable for a short-range interaction. Of particular conceptual interest would thus be a system where a control parameter alpha allows to continuously switch on and off the Efimov effect. When alpha crosses the critical value alpha_c the system would then exhibit an intriguing transition from a finite number to an infinite number of trimer states. However Efimov's universal theory alone cannot in principle fully characterize this transition, as it cannot predict the behavior of the three-body parameter nor the energy of the ground state trimer.
With cold atoms, one may realize such a system, with two same-spin-state fermions of mass m resonantly interacting with a lighter impurity of mass M. Then the mass ratio alpha=m/M constitutes the desired knob controlling the Efimov effect, with alpha_c=13.6069... When the impurity-fermion resonant interaction is realized on an ultra-narrow Feshbach resonance, a fully microscopic model can be used, as proposed by Petrov, involving the so-called Feshbach length R_*, an effective range for the interaction.
Extending to fermions a technique developed by Mora, Gogolin, Egger for bosons, one can then determine analytically the three-body parameter and fully characterize the emergence of the infinite number of trimer states beyond alpha=alpha_c.
Author
M.
Yvan Castin
(CNRS)
