Phonons in an optical lattice

Yutaka Shikano, Hiroya Sasaki, Riho Tanaka +4 more

Vyacheslav I. Yukalov, K. Ziegler

The influence of collective phonon excitations, due to intersite atomic interactions, on the stability of optical lattices is analyzed. These phonon excitations are shown to essentially reduce the ability of atoms to be localized. The states that seem to be insulating in the absence of the phonon excitations can become delocalized when the latter are present. The delocalization effect exists for both long-range as well as local atomic interactions.

Georg A. Raithel, G. Birkl, William D. Phillips +1 more

Benjamin Lev, Brendan Marsh

Quantized sound waves---phonons---govern the elastic response of crystalline materials, and also play an integral part in determining their thermodynamic properties and electrical response (e.g., by binding electrons into superconducting Cooper pairs). The physics of lattice phonons and elasticity is absent in simulators of quantum solids constructed of neutral atoms in periodic light potentials: unlike real solids, traditional optical lattices are silent because they are infinitely stiff. Optical-lattice realizations of crystals therefore lack some of the central dynamical degrees of freedom that determine the low-temperature properties of real materials. We will discuss our creation of an optical lattice with phonon modes using a Bose-Einstein condensate (BEC) coupled to a confocal optical resonator.

M. Bruderer, T. H. Johnson, Stephen R. L. Clark +3 more

We present an analysis of Bose-Fermi mixtures in optical lattices for the case where the lattice potential of the fermions is tilted and the bosons (in the superfluid phase) are described by Bogoliubov phonons. It is shown that the Bogoliubov phonons enable hopping transitions between fermionic Wannier-Stark states; these transitions are accompanied by energy dissipation into the superfluid and result in a net atomic current along the lattice. We derive a general expression for the drift velocity of the fermions and find that the dependence of the atomic current on the lattice tilt exhibits negative differential conductance and phonon resonances. Numerical simulations of the full dynamics of the system based on the time-evolving block decimation algorithm reveal that the phonon resonances should be observable under the conditions of a realistic measuring procedure.

Aikaterini Mandilara, Zoran M. Ivić, Dalibor Čevizović +1 more