Optical lattice

Atoms (represented as blue spheres) pictured in a 2D-optical lattice potential (represented as the yellow surface).

An optical lattice is formed by the interference of counter-propagating laser beams, creating a spatially periodic polarization pattern. The resulting periodic potential may trap neutral atoms via the Stark shift.[1] Atoms are cooled and congregate at the potential extrema (at maxima for blue-detuned lattices, and minima for red-detuned lattices). The resulting arrangement of trapped atoms resembles a crystal lattice[2] and can be used for quantum simulation.

Atoms trapped in the optical lattice may move due to quantum tunneling, even if the potential well depth of the lattice points exceeds the kinetic energy of the atoms, which is similar to the electrons in a conductor.[3] However, a superfluid–Mott insulator transition[4] may occur, if the interaction energy between the atoms becomes larger than the hopping energy when the well depth is very large. In the Mott insulator phase, atoms will be trapped in the potential minima and cannot move freely, which is similar to the electrons in an insulator. In the case of fermionic atoms, if the well depth is further increased the atoms are predicted to form an antiferromagnetic, i.e. Néel state at sufficiently low temperatures.[5]

  1. ^ Grimm, Rudolf; Weidemüller, Matthias; Ovchinnikov, Yurii B. (2000), "Optical Dipole Traps for Neutral Atoms", Advances In Atomic, Molecular, and Optical Physics, Elsevier, pp. 95–170, arXiv:physics/9902072, doi:10.1016/s1049-250x(08)60186-x, ISBN 978-0-12-003842-8, S2CID 16499267, retrieved 2020-12-17
  2. ^ Bloch, Immanuel (October 2005). "Ultracold quantum gases in optical lattices". Nature Physics. 1 (1): 23–30. Bibcode:2005NatPh...1...23B. doi:10.1038/nphys138. S2CID 28043590.
  3. ^ Gebhard, Florian (1997). The Mott metal-insulator transition models and methods. Berlin [etc.]: Springer. ISBN 978-3-540-61481-4.
  4. ^ Greiner, Markus; Mandel, Olaf; Esslinger, Tilman; Hänsch, Theodor W.; Bloch, Immanuel (January 3, 2002). "Quantum phase transition from a superfluid to a Mott insulator in a gas of ultracold atoms". Nature. 415 (6867): 39–44. Bibcode:2002Natur.415...39G. doi:10.1038/415039a. PMID 11780110. S2CID 4411344.
  5. ^ Koetsier, Arnaud; Duine, R. A.; Bloch, Immanuel; Stoof, H. T. C. (2008). "Achieving the Néel state in an optical lattice". Phys. Rev. A. 77 (2): 023623. arXiv:0711.3425. Bibcode:2008PhRvA..77b3623K. doi:10.1103/PhysRevA.77.023623. S2CID 118519083.