2006/01/31 by W. Vincent Liu, Congjun Wu · 1 citation
Physics and Astronomy · #cond-mat.other #cond-mat.str-el
paper · pdf · doi:10.1103/physreva.74.013607
published as Phys. Rev. A 74, 013607 (2006) · 10 pages, 7 figures (with one in Appendix); added references and reorganized appendices in REVTeX
arxiv created 2006/06/15 · arxiv updated 2009/12/01
The paradigm of Bose-Einstein condensation has been associated with zero momentum to which a macroscopic fraction of bosons condense. Here we propose a new quantum state where bosonic alkali-metal atoms condense at non-zero momenta, defying the paradigm. This becomes possible when the atoms are confined in the p-orbital Bloch band of an optical lattice rather than the usual s-orbital. The new condensate simultaneously forms an order of transversely staggered orbital currents, reminiscent of orbital antiferromagnetism or d-density wave in correlated electronic systems but different in fundamental ways. We discuss several approaches of preparing atoms to the p-orbital and propose an ``energy blocking'' mechanism by Feshbach resonance to protect them from decaying to the lowest s-orbital. Such a model system seems very unique and novel to atomic gases. It suggests a new concept of quantum collective phenomena of no prior example from solid state materials.