Ground-state properties of the hydrogen chain: insulator-to-metal transition, dimerization, and magnetic phases

Accurate and predictive computations of the quantum-mechanical behavior of many interacting electrons in realistic atomic environments are critical for the theoretical design of materials with desired properties. Such computations require the solution of the grand-challenge problem of the many-electron Schrodinger equation. An infinite chain of equispaced hydrogen atoms is perhaps the simplest realistic model for a bulk material, embodying several central characters of modern condensed matter physics and chemistry, while retaining a connection to the paradigmatic Hubbard model. Here we report the combined application of different cutting-edge computational methods to determine the properties of the hydrogen chain in its quantum-mechanical ground state. Varying the separation between the nuclei mimics applying pressure to a crystal, which we find leads to a rich phase diagram, including an antiferromagnetic Mott phase, electron density dimerization with power-law correlations, an insulator-to-metal transition and an intricate set of intertwined magnetic orders. Our work highlights the importance of the hydrogen chain as a model system for correlated materials, and introduces methodologies for more general studies of the quantum many-body problem in solids.