Pinning quantum phase transition for a Luttinger liquid of strongly interacting bosons
Abstract
Quantum manybody systems can have phase transitions even at zero temperature; fluctuations arising from Heisenberg's uncertainty principle, as opposed to thermal effects, drive the system from one phase to another. Typically, during the transition the relative strength of two competing terms in the system's Hamiltonian changes across a finite critical value. A wellknown example is the MottHubbard quantum phase transition from a superfluid to an insulating phase, which has been observed for weakly interacting bosonic atomic gases. However, for strongly interacting quantum systems confined to lowerdimensional geometry, a novel type of quantum phase transition may be induced and driven by an arbitrarily weak perturbation to the Hamiltonian. Here we observe such an effectthe sineGordon quantum phase transition from a superfluid Luttinger liquid to a Mott insulatorin a onedimensional quantum gas of bosonic caesium atoms with tunable interactions. For sufficiently strong interactions, the transition is induced by adding an arbitrarily weak optical lattice commensurate with the atomic granularity, which leads to immediate pinning of the atoms. We map out the phase diagram and find that our measurements in the strongly interacting regime agree well with a quantum field description based on the exactly solvable sineGordon model. We trace the phase boundary all the way to the weakly interacting regime, where we find good agreement with the predictions of the onedimensional BoseHubbard model. Our results open up the experimental study of quantum phase transitions, criticality and transport phenomena beyond Hubbardtype models in the context of ultracold gases.
 Publication:

Nature
 Pub Date:
 July 2010
 DOI:
 10.1038/nature09259
 arXiv:
 arXiv:1004.3168
 Bibcode:
 2010Natur.466..597H
 Keywords:

 Condensed Matter  Quantum Gases
 EPrint:
 Nature 466, 597 (2010)