Nematic and Antiferromagnetic Quantum Criticality in a Multi-Orbital Hubbard Model for Iron Pnictides

Abstract

The extent to which quantum criticality drives the physics of iron pnictides is a central question in the field. Earlier theoretical considerations were based on an effective field theory, and the proposed realization in P-doped iron arsenides has received extensive experimental evidence. To connect the quantum critical behavior with the underlying electronic physics, it is important to analyze it within microscopic models. Here, we do so for a multi-orbital model containing both Hubbard and Hund's interactions, by a variational Monte Carlo method based on Jastrow-Slater wave functions that allow for a non-perturbative treatment of electron correlations. We find strong evidence for the existence of a unique quantum critical point, where both nematic and (π, 0) antiferromagnetic orders develop together, in the bad-metal regime of the phase diagram. Implications of our results for the iron-based superconductivity are discussed.

Fragile Insulator and Electronic Nematicity in a Graphene Moire System

“…As in Ref. 29, a spin Jastrow factor is used, in addition to the usual density Jastrow factor, to treat the correlation effect of the Hund's coupling. The uncorrelated state |Φ 0 is specified by the following auxiliary (quadratic) Hamiltonian 41,42 :…”

“…Here, we investigate this regime using non-perturbative methods. Our primary tool will be the recently developed Variational Monte Carlo (VMC) method that incorporates the correlation effects of not only the Hubbard interaction but also the Hund's coupling 29 (see Methods).…”

“…We next analyse the possible electronic orders, including nematicity. The effect of onsite interactions is studied using the VMC method that is non-perturbative in both the Hubbard interaction and Hund's coupling 29 (see Methods). In the intermediate correlation regime, we find that the ground state has a collinear antiferromagnetic (CAFM) order (Fig.…”