Instability of insulating states in optical lattices due to collective phonon excitations

Abstract

The role of collective phonon excitations on the properties of cold atoms in optical lattices is investigated. These phonon excitations are collective excitations, whose appearance is caused by intersite atomic interactions correlating the atoms, and they do not arise without such interactions. These collective excitations should not be confused with lattice vibrations produced by an external force. No such a force is assumed. But the considered phonons are purely self-organized collective excitations, characterizing atomic oscillations around lattice sites, due to intersite atomic interactions. It is shown that these excitations can essentially influence the possibility of atoms to be localized. The states that would be insulating in the absence of phonon excitations can become delocalized when these excitations are taken into account. This concerns long-range as well as local atomic interactions. To characterize the region of stability, the Lindemann criterion is used.

Latex file, 27 pages, 1 figure

References in corpus (7)

• Many-Body Physics with Ultracold Gases
• Quantum phase transition from a superfluid to a Mott insulator in a gas of ultracold atoms
• Bose-Einstein condensation of chromium
• Bose-Einstein Condensation of Erbium
• Cold Bosons in Optical Lattices
• Frequency splitting of intervalley phonons in graphene
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Cited by in corpus (6)

• Bose-Einstein condensation temperature of weakly interacting atoms
• Destiny of optical lattices with strong intersite interactions
• Models of Mixed Matter
• Melting of electronic and excitonic crystals in 2D semiconductor moiré patterns: a perspective from the Lindemann criterion
• Unified theory of quantum crystals and optical lattices with Bose-Einstein condensate
• Nanoscale Phase Separation in Ferroelectric Materials