Figure 1: Site-occupancy resolving laser spectroscopy.
(a) Energy diagram of singly and doubly occupied sites in an optical lattice. The doubly occupied sites have energy shifts due to on-site interactions, which depend on the atomic state. (b) The relevant energy scales in the laser spectroscopy (see the text). The vertical dashed line denotes the critical lattice depth of the Mott transition30 according to the mean-field theory for a homogeneous system. (c) The site-occupancy resolved spectrum in a deep lattice. The large attractive interaction of Uge,0 gives sidebands corresponding to the excitations in the multiple occupied sites on the negative frequency side. Error bars indicate s.e.m., and the solid line denotes a triple Gaussian fit to the data. Note that we only observe a single resonance peak even for multiply occupied sites due to a collisional blockade effect. (d) Separately induced Rabi oscillations. The observed Rabi frequencies are 2.1, 2.7 and 2.8 kHz for the singly, doubly and triply occupied sites, respectively. The lattice depth is 22Er in c,d. The experimental details can be found in Supplementary Note 2.
