Atom-Hole BECs

Atom-hole BECs, condensates of atom-hole pairs held in an "optical lattice" made of crossed laser beams, might contribute to the now-popular program of putting quantum weirdness to use in information processing and to the study of superfluids through the use of tailored interactions.

Chaohong Lee, a physicist at the Max Planck Institute for the Physics of Complex Systems in Dresden, has suggested his model of atom-hole condensates in analogy with electron-hole clouds in semiconductors. When an electron is sprung from its niche in a semiconductor crystal, the hole remaining behind can itself move around and act as if it were a positively charged object. Indeed, a nearby electron and hole can behave as a sort of pair. These pairs, or "excitons," can condense into a single quantum state. In light emitting diodes (LEDs) the coalescence of holes and electrons results in light emission.

Lee believes the same can happen to supercold Fermi atoms (those with a half-integral amount of spin) lodged in all, or nearly all, the interstices of an optical lattice. In his model two species---with different magnetic polarizations---of the same element would be loaded in the trap. Then, by altering an applied magnetic field, interactions among the trapped atoms, and the potential depth of the optical lattice could be manipulated so as to favor atom-hole pair formation and even condensation. Like the electron-hole partners meeting to create light, the atom-hole mates might also be made to render light in novel ways.(Physical Review Letters, upcoming article; 49-871-2124, chlee@mpipks-dresden.mpg.de)