Spectral weight redistribution in strongly correlated bosons in optical lattices

Year: 2008

Authors: Menotti C., Trivedi N.

Autors Affiliation: ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, E-08860 Castelldefels (Barcelona), Spain;
Dipartimento di Fisica and CNR-INFM-BEC, Universita’ di Trento, I-38050 Povo (Trento), Italy;
Department of Physics, Ohio State University, Columbus, Ohio 43210, USA

Abstract: We calculate the single-particle spectral function for the one-band Bose-Hubbard model within the random- phase approximation RPA. In the strongly correlated superfluid, in addition to the gapless phonon excitations, we find extra gapped modes, which become particularly relevant near the
superfluid-Mott quantum phase transition QPT. The strength in one of the gapped modes, a precursor of the Mott phase, grows as the QPT is approached and evolves into a hole particle excitation in the Mott insulator depending on whether the chemical potential is above below the tip of the lobe. The sound
velocity c of the Goldstone modes remains finite when the transition is approached at constant density; otherwise, it vanishes at the transition. It agrees well with Bogoliubov theory except close to the transition. We also calculate the spatial correlations for bosons in an inhomogeneous trapping
potential creating alternating shells of Mott insulator and superfluid. Finally, we discuss the capability of the RPA to correctly account for quantum fluctuations in the vicinity of the QPT.


Volume: 77 (23)      Pages from: 235120-1  to: 235120-13

KeyWords: Bose Hubbard model; excitations;
DOI: 10.1103/PhysRevB.77.235120

Citations: 71
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