| 概 要 |
Ultracold atoms in an optical lattice can be well described by the Hubbard model, which is a fundamental theoretical model for strongly-correlated electrons in solids. Despite its simplicity, it contains diverse many-body phenomena such as magnetism and superconductivity.
One of natural extensions of the Hubbard model is to enlarge its spin symmetry to SU(N>2).
Large spin symmetry enhances quantum fluctuations, which makes the phase diagram of the SU(N) model completely different from the SU(2) case.
>In this talk, we present the experimental realization of the SU(N) Hubbard model using ultracold Fermi gases of ytterbium atoms in an optical lattice. Yb exhibits SU(2I+1) spin symmetry originating from its nuclear spin I. We successfully realize the SU(6) Hubbard model with 173Yb (I=5/2) and even the SU(2)×SU(6) model with 171Yb-173Yb mixture [1].
Accessing the low temperature regime where strong correlation plays role is a challenging task for fermionic optical lattice systems.
We find that the large entropy carried by SU(6) spin of 173Yb enhances adiabatic cooling in the lattice loading process, which enables to achieve the Mott insulating phase in a deep optical lattice [2]. Based on double occupancy measurement, we perform a series of experiments to characterize an SU(N) Mott insulator: compressibility measurement, probing charge gap, and nearest neighbor correlations.
The realization of this novel Mott state will open up the possibilities to investigate exotic SU(N) quantum phases with ultracod atoms in optical lattices.
[1] S. Taie et al., Phys. Rev. Lett. 105, 050405 (2010).
[2] S. Taie et al., Nature Phys. 8, 825 (2012).
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