Fig. 6: Experimental proposal.

a A device architecture for realizing and probing the topological phase transition of the SSH model. A chain of STM-fabricated dopant atoms, or gate defined quantum dots, is positioned in the center of a collection of electrodes and gates. The source and the drain leads are used for measuring the current of the electrons tunneling from the source, through the many-body state of the chain, to the drain. Since the source and the drain are close to the edges, the conductance is proportional to the charge excitation density at the edge of the many-body state (see text). The A side gates are used for tuning the on-site energy, and thus the chemical potential. The B side gates between the sites are used to control the hopping amplitudes. b The conductance spectrum at kT = 0.02 as a function of the chemical potential for Δt = 0.5 (solid red) and Δt = −0.5 (dotted blue) at zero field (top panel) and at a field strength just above the critical value (bottom panel). The spectrum for both values of Δt shows the lower Hubbard band (LHB) and upper Hubbard band (UHB) separated by the Mott gap, and each band is further separated by the charge excitation gap at quarter-filling. For Δt > 0, there is a conductance peak in the middle of this gap due to the tunneling through the edge states of the charge excitation. The formation of the strongly localized edge state in the SSH model above the critical field strength leads to a sharp increase in the conductance peak at quarter-filling in the bottom panel. c Density plot of the conductance around quarter-filling, showing the sharp increase of the peak at the critical field strength. All energies are scaled by the average value of the two hopping amplitudes.