Insight into the many-electron wavefunction of Mott-insulating antiferromagnets

We investigate the structure of full configuration-interaction wave functions of a prototypical Mott-insulating anti-ferromagnet using a state-of-the-art methodology (FCIQMC). We show that the compactness of the wavefunctions depends dramatically and counterintuitively on the nature of the single-particle representation, with restricted Hartree-Fock (HF) yielding a much more compact solution than unrestricted HF, and which furthermore may be amenable to approximation. Our study suggests that in a suitable basis, powerful quantum chemical methodologies may be employed in describing such systems.