# Strongly correlated double Dirac fermions

## TL;DR

This study explores how strong electron interactions influence the stability of double Dirac fermions in Bi$_2$CuO$_4$, revealing their persistence until magnetic order breaks the symmetry, with pressure as a potential tuning parameter.

## Contribution

It combines ab-initio and dynamical mean field theory to analyze the interplay of topology and correlations in double Dirac fermions within a realistic material model.

## Key findings

- Double Dirac dispersion persists under strong correlations.
- Magnetic ordering breaks the symmetry and destroys the Dirac fermions.
- Pressure can potentially realize a double-Dirac metal in Bi$_2$CuO$_4$.

## Abstract

Double Dirac fermions have recently been identified as possible quasiparticles hosted by three-dimensional crystals with particular non-symmorphic point group symmetries. Applying a combined approach of ab-initio methods and dynamical mean field theory, we investigate how interactions and double Dirac band topology conspire to form the electronic quantum state of Bi$_2$CuO$_4$. We derive a downfolded eight-band model of the pristine material at low energies around the Fermi level. By tuning the model parameters from the free band structure to the realistic strongly correlated regime, we find a persistence of the double Dirac dispersion until its constituting time reveral symmetry is broken due to the onset of magnetic ordering at the Mott transition. We analyze pressure as a promising route to realize a double-Dirac metal in Bi$_2$CuO$_4$.