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

The extent to which quantum criticality drives the physics of iron pnictides is a central question in the field. While the issue had been addressed by effective field theories [1,2], how to approach it in the multi-orbital Hubbard model has been a long-standing challenge due to the limitation in methods for intermediate correlations. Here [3] we study this problem within a multi-orbital Hubbard model containing both the 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 the electron correlations. We find strong evidence for the existence of a unique quantum critical point, where both nematic and (π, 0) antiferromagnetic orders develop, in the bad-metal regime of the phase diagram. A robust signal for unconventional superconducting pairing is also found as the system approaches the quantum critical point from the paramagnetic side.

[1] J. Dai, Q. Si, J. X. Zhu, and E. Abrahams, PNAS 106, 4118, (2009).
[2] J. Wu, Q. Si and E. Abrahams, Phys. Rev. B 93, 104515 (2016).
[3] W.-J. Hu, L. Chen, H. Hu, R. Yu, H.-H. Lai, L. F. Tocchio, F. Becca, Q. Si, arXiv:1903.12625.