We study quantum many-body system with orbital degrees of freedom using ultracold atomic gases in an optical lattice. Recently, alkaline-earth-like atoms such as ytterbium (Yb) have been received much attention as an experimental platform for quantum simulation with orbital degrees of freedom owing to the existence of the metastable state 3P0 and 3P2 as well as the ground state 1S0. Using Yb atoms in the 1S0 and 3P0 states in a state-dependent optical lattice as shown in the figure, we are developing a novel quantum simulator which is beyond the single-band Hubbard model.
One of our projects is the quantum simulation of the Kondo effect, which arises from an antiferromagnetic spin-exchange interaction between conduction electron and a localized magnetic moment. It was originally studied in the context of the enhancement of the electrical resistivity in magnetic alloy at low temperature, and this is the central problem in condensed matter physics. Also, the Kondo lattice model, where localized spins are aligned periodically, includes rich physics in the vicinity of the quantum critical point between the RKKY ordered phase and the Kondo screening phase.
So far, we measured the interorbital interaction energies of fermionic isotope of 171Yb, indicating that the interorbital spin-exchange interaction is antiferromagnetic (K. Ono et al., PRA (2019)). The result suggests that the two-orbital system using 171Yb is a promising candidate for the quantum simulator for the Kondo physics.
