Spectral function calculations for subsidiary-boson methods

Strong and localized electron interactions are typically described by the Hubbard model and its extensions, which are analytically solvable only in a few special or simplified cases. To obtain results for more complex or realistic situations, we must employ approximate numerical methods. We use subsidiary-boson (or slave-boson) methods because they are computationally more efficient than gold-standard methods such as DMRG and DMFT, allowing us to study larger systems or achieve converged results more rapidly. Typical subsidiary-boson calculations focus on the electronic ground state, but calculating spectral functions is essential for making direct comparisons with spectroscopic measurements as they provide detailed information about electronic excitations. Here, we present a formalism for calculating the one-electron spectral functions via the single-site subsidiary-boson method, which we have implemented in the latest release of our free, open-source subsidiary-boson software BoSS [1] (bitbucket.org/yalebosscode/boss). We demonstrate applications to transition metal oxides.

[1] A. Georgescu, M. Kim and S. Ismail-Beigi, Comp. Phys. Comm. 265, 107991 (2021). DOI 10.1016/j.cpc.2021.107991