Charge Doping and Quantum Monte Carlo of NiO

NiO is a widely studied model Mott insulator that orders antiferromagnetically below 520 K. The Ni spins align ferromagnetically within the (1,1,1) planes of the NaCl structure and antiferromagnetically between those planes. The transition temperature drops with Li doping and the system becomes first ferrimagnetic and later again antiferromagnetic with a Néel temperature of 9 K. Despite the intense study of NiO and other Mott insulators, the evolution of electronic correlations upon charge doping, which gives rise to a plethora of spectacular phenomena (including superconductivity in cuprates) is poorly understood to date. In a new effort, combining Quantum Monte Carlo (QMC) with thin film growth of charge-doped NiO, we address this question. We analyze the band gap with spectroscopic ellipsometry as a function of doping and strain and compare the results to QMC. This will lead to a better understanding of the electronic correlations that bring about charge or magnetic order or superconductivity.