Molecular Bose-Einstein condensates, resonance chemistry, and enhancement of weak interactions

V. V. Flambaum, J. S. M. Ginges

Collisions and chemical reactions of molecules in Bose-Einstein condensates (BECs) are extremely sensitive to weak fields. This sensitivity arises due to the high density of compound resonances and a macroscopic number of molecules with kinetic energy E=0 (perfect energy resolution). We suggest that chemical reactions in molecular BECs could be used to enhance effects produced by small external perturbations and search for a parity-violating energy difference in chiral molecules.

V. V. Flambaum, J. S. M. Ginges

With the creation of ultracold atoms and molecules, a new type of chemistry---``resonance'' chemistry---emerges: chemical reactions can occur when the energy of colliding atoms and molecules matches a bound state of the combined molecule (Feshbach resonance). This chemistry is rather similar to reactions that take place in nuclei at low energies. In this paper we suggest some problems for future experimental and theoretical work related to the resonance chemistry of ultracold molecules. Molecular Bose-Einstein condensates are particularly interesting because in this system collisions and chemical reactions are extremely sensitive to weak fields; also, a preferred reaction channel may be enhanced due to a finite number of final states. The sensitivity to weak fields arises due to the high density of narrow compound resonances and the macroscopic number of molecules with kinetic energy $E=0$ (in the ground state of a mean-field potential). The high sensitivity to the magnetic field may be used to measure the distribution of energy intervals, widths, and magnetic moments of compound resonances and study the onset of quantum chaos. A difference in the production rate of right-handed and left-handed chiral molecules may be produced by external electric $\mathbf{E}$ and magnetic $\mathbf{B}$ fields and the finite width $\ensuremath{\Gamma}$ of the resonance (correlation $\ensuremath{\Gamma}\mathbf{E}∙\mathbf{B}$). The same effect may be produced by the parity-violating energy difference in chiral molecules.

Johannes Hecker Denschlag

Hongchao Li, Xie-Hang Yu, Masaya Nakagawa +1 more

Motivated by recent experimental realization of a Bose-Einstein condensate (BEC) of dipolar molecules, we develop superfluid transport theory for a dissipative BEC to show that a weak uniform two-body loss can induce phase rigidity, leading to superfluid transport of bosons without repulsive interactions. A generalized f-sum rule is shown to hold for a dissipative superfluid as a consequence of weak U(1) symmetry. We also demonstrate that dissipation enhances the stability of a molecular BEC with dipolar interactions. Possible experimental signatures of dissipative superfluidity are discussed.