Unleashing antiferromagnetic fluctuations for charge and spin responses of pseudo-spin-half square-lattice

While manipulation of antiferromagnetic (AFM) order arises to the forefront of spintronics, it is a long-standing fundamental problem lying at the heart of correlated electron physics. Here we will present a series of exciting findings in pseudo-spin-half square-lattice systems, which are implemented as artificial layered iridates [(SrIrO₃)₁/(SrTiO₃)_m] to engage with a staggered magnetic field effect (STMF) due to strong spin-orbit interaction. By tuning the SrTiO₃ spacer, the AFM structure of the Mott insulating state can be engineered [Phys. Rev. Lett. 119, 027204 (2017)]. With m = 1, the STMF leads to an intriguing positive anomalous magnetoresistance that probes the AFM susceptibility, because of the strong interplay between charge and longitudinal spin fluctuations [Nat. Commun. Accepted (2019)]. Upon driving the AFM structure to the two-dimensional limit at m = 2, while the ordering temperature is significantly reduced by strong critical fluctuations, the STMF allows an external field of only a thousandth of the superexchange interaction to greatly suppress the AFM fluctuations and enable a giant response of the AFM order [Nat. Phys. 14, 806 (2018)].