Exciton transport in a 2×4 Ge quantum dot ladder device

Analog fermionic quantum simulators can give insight into complicated many-body quantum phenomena beyond the capabilities of classical computers. Among the available platforms, semiconductor quantum dot systems excel for their in-situ tunability, thermal energies lower than any other relevant energy scale and the naturally occurring long-range Coulomb interaction. The latter is particularly relevant for several exotic states of matter, from Wigner crystals to excitonic insulators. Here, we present the control of a 2×4 quantum dot device embedded in a Ge/SiGe heterostructure. Individual gates for the control of tunnel couplings and site occupations allow us to tune the device into the single charge regime and explore exciton formation and transport enabled by the long-range Coulomb interaction. We demonstrate control of the tunnel couplings between all the dots and tune the device into two separate 1D channels: a drive channel and a drag channel. While the tunneling between the channels is suppressed, we still retain a sizable Coulomb interaction which favors exciton formation. Through charge sensing, we are able to detect the position of all the charges at any point in time and quantify the Coulomb interaction strength. We then purposefully transfer single charges in the drive channel and, in the right conditions, observe that a charge of opposite sign is carried along in the drag channel. This signature of exciton transport opens the possibility for the exploration of exciton condensation and could give insight into the mechanisms governing their formation. Moreover, our experiment positions quantum dot systems as a unique candidate for the simulation of complex phases of matter governed by the long-range Coulomb interaction.