Electron Model Captured by Atom Pair

Understanding and creating models that explain how electrons move and interact in metals has been at the heart of theoretical and experiment efforts for nearly 100 years. One approach to probing these systems is to devise a simple mathematical model of the electrons, which pares down the complexity of the system to its most basic elements. The Fermi-Hubbard model is one such model. It reduces electron behavior to two actions: a hopping motion between sites in the metal lattice and an interaction between electrons. The hope is that, despite the model’s simplicity, it might capture observed behaviors, such as a metal’s transition to being insulating or magnetic. However, the predictions—even of a simple model—become mathematically prohibitive for large numbers of electrons. This leaves experiment as a key tool for testing theories, such as the Fermi-Hubbard model, by simulating them with real particles that are easier to control than electrons inside metals [1]. Simon Murmann and his colleagues at the University of Heidelberg, Germany, have created tunable, tailored environments in which two fermionic atoms display key components of the Fermi-Hubbard model [2].