Altermagnetism on the Shastry-Sutherland lattice

Abstract: Motivated by recent developments on altermagnetism, we investigate the Hubbard model on the Shastry-Sutherland lattice, where the onsite repulsion between electrons induces the onset of a staggered magnetic order in which opposite magnetic sublattices are related to each other only by rotations and glide reflections, and not by inversion nor translations. As a consequence, the magnetic phase displays an altermagnetic character, i.e. a finite (non-relativistic) Zeeman splitting of the electronic excitations, despite the absence of a net magnetization. By means of a variational Monte Carlo approach based on Jastrow-Slater wave functions, which accounts for electronic correlations beyond the single-particle approximation, we study how $d$-wave altermagnetism shows up in the ground state properties and in the spectral function of the system. We characterize the metal-insulator transition between altermagnetic phases at half-filling and the stability of altermagnetism as a function of doping. The calculation of the single-particle spectral function displays the spin-split nature of the electronic excitations, also within the Mott insulating regime. We discuss possible realizations of the model in the context of organic $\alpha$- or $\kappa$-(BEDT-TTF)$_2$X charge transfer salts.