Quantum Simulation of Excitons with Dipolar Fermi Gases in Optical Lattices

Ultracold atoms have emerged as a powerful platform for simulating condensed matter phenomena, offering insights into phenomena difficult to analyze in detail in solid-state systems. Inspired by the fast progress on the study of exciton physics in atomically thin, transition metal dichalcogenide (TMD) semiconductors, we here investigate the formation of analogs of excitons in cold atomic systems comprised of single-component fermions with strong dipolar interactions. In order to directly simulate the physics of TMD, we consider ultracold ground-state molecules or dipolar atoms in a hexagonal optical lattice. Using an energy offset between trigonal sub-lattices opens up a band gap with degeneracies at the K/K' points of the first Brillioun zone. Based on a variational approach, we predict the existence of cold atomic excitons comprised of bound atom-hole pairs. We demonstrate how these excitons can be excited using lattice modulation spectroscopy, and we show that both time-of-flight spectroscopy and high-resolution quantum gas microscopy can be used to map out the exciton wavefunction. Establishing the core idea of how to simulate semiconductor physics in cold atoms, this work lays the foundation for studies of complex electronic states governing semiconductors, including trions, polarons, exciton insulators and condensates.