Charge conjugation symmetries, where a particle is replaced with its antiparticle, are playing a big role in physics. In solid state materials, which are described by a periodic lattice potential, a similar symmetry can be found between an occupied and an unoccupied lattice site, a hole.

We could show experimentally, that this symmetry (a) is also valid in strongly interacting fermi-gasses in periodic optical potentials (b). Furthermore, we laid out the possibility how this insight could be used to explore further the phase diagram of the two-dimensional Hubbard model (c), which could be key to understanding the high-temperature superconductivity.  

Reference: Gall, M., Chan, C. F., Wurz, N., & Köhl, M. (2020). Simulating a Mott insulator using attractive interaction. Physical Review Letters, 124(1), 010403.