Abstract
Bose-Einstein condensates (BECs) of positronium (Ps) have been of experimental and theoretical interest due to their potential application as the gain medium of a -ray laser. Ps BECs are intrinsically spinor due to the presence of ortho-positronium (-Ps) and para-positronium (-Ps), whose annihilation lifetimes differ by three orders of magnitude. In this paper, we study the spinor dynamics and annihilation processes in the -Ps/-Ps system using both solutions of the time-dependent Gross-Pitaevskii equations and a semiclassical rate-equation approach. The spinor interactions have an O(4) symmetry which is broken to SO(3) by an internal energy difference between -Ps and -Ps. For an initially unpolarized condensate, there is a threshold density of cm at which spin mixing between -Ps and -Ps occurs. Beyond this threshold, there are unstable spatial modes accompanied by spin mixing. To ensure a high production yield above the critical density, a careful choice of external field must be made to avoid the spin mixing instability.
2 More- Received 21 February 2014
DOI:https://doi.org/10.1103/PhysRevA.89.043624
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