Strong pairing in mixed dimensions

Among the key motivations for the development of quantum simulation experiments using ultra cold atoms is the goal to understand the Fermi-Hubbard model, and in particular identifying a possible pairing mechanism which could lead to high-temperature superconductivity. In this talk, I will present a string-based binding mechanism, which leads to high temperature pairing of fermions in a microscopically repulsive model. In particular, I will introduce a general, highly efficient pairing mechanism for mobile dopants in antiferromagnetic Mott insulators, which leads to binding energies proportional to $t^{1/3}$, where $t$ is the hopping amplitude of the charge carriers. The pairing is caused by the energy that one charge gains when retracing a string of frustrated bonds created by another charge. I will show that this mechanism leads to the formation of highly mobile, but tightly bound pairs in the case of mixed-dimensional Fermi-Hubbard bilayer systems. 

This setting is closely related to the Fermi-Hubbard model believed to capture the physics of copper oxides, and can be realized in ultracold atom experiments. In particular, due to the large binding energies, pairing can be experimentally observed at currently achievable temperatures.