FIG. 18.

Two-band spectrum of the SSH Hamiltonian and Zak phase measurement. An initial wave packet is prepared at the bottom of the lowest band (left column). Each atom is in the superposition of the $|\pm \rangle$ spin states, which experience opposite forces in the presence of a magnetic field gradient. After a combination of exchanges of the atomic internal state and of the dimerization (middle column), the two wave packets recombine at the top of the highest band (right column). The measurement of the accumulated phase provides the value of the Zak phase. From Atala et al., 2013.