Abstract
We theoretically analyze the response properties of ultracold bosons in optical lattices to the static variation of the trapping potential. We show that, upon an increase of such a potential (trap squeezing), the density variations in a central region, with linear size of ≲10 wavelengths, reflect that of the bulk system upon changing the chemical potential: hence measuring the density variations gives direct access to the bulk compressibility. When combined with standard time-of-flight measurements, this approach has the potential of unambiguously detecting the appearance of the most fundamental phases realized by bosons in optical lattices, with or without further external potentials: superfluid, Mott insulator, band insulator and Bose glass.
Highlights
Ultracold gases in optical lattices offer the unique opportunity of literally implementing fundamental lattice models of strongly correlated quantum many-body systems, either bosonic or fermionic, traditionally considered as ”toy” models for the description of complex condensed matter systems [1, 2]
When combined with standard time-of-flight measurements, this approach has the potential of unambiguously detecting the appearence of the most fundamental phases realized by bosons in optical lattices, with or without further external potentials: superfluid, Mott insulator, band insulator and Bose glass
In the particular case of ultracold bosons realizing the Bose-Hubbard (BH) model, recent experimental developments have led to the spectacular demonstration of the Mott insulating (MI) phase with controllable filling [3, 4, 5], and even more recent developments in laser trapping offers the possibility of realizing further fundamental insulating phases, such as a band insulator (BI) in a commensurate superlattice [6] or a Bose glass (BG) in an incommensurate superlattice or in a laser-speckle potential [7, 8]
Summary
Ultracold gases in optical lattices offer the unique opportunity of literally implementing fundamental lattice models of strongly correlated quantum many-body systems, either bosonic or fermionic, traditionally considered as ”toy” models for the description of complex condensed matter systems [1, 2].
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