*Abstract:

 Due to the robustness against external   magnetic fields and ultrafast dynamics, antiferromagnets are essential for   next-generation spintronic devices. To achieve this goal, the   antiferromagnetic order needs to be detected and manipulated efficiently.   Through the linear dichroism and anisotropic magnetoresistance, the spatial   orientation of the antiferromagnetic order can be probed. However, both   methods are insensitive to the reversal of the antiferromagnetic order. In   this talk, we consider two types of nonlinear nonreciprocal effects: the   intrinsic nonlinear Hall effect and the nonreciprocal directional dichroism.   Both of them are sensitive to the time reversal symmetry but insensitive to   the combined TI symmetry. Therefore, they can be used to probe the reversal   of the antiferromagnetic order. Further analysis shows that they are deeply   related to the quantum metric and Berry curvature, suggesting intimate   connection between the macroscopic antiferromagnetic order and microscopic   geometrical properties. This connection offers efficient tuning methods   through the Berry curvature/quantum metric engineering.

*Profile：

Dr. Yang Gao received his bachelor degree   from Peking University, and doctorate from University of Texas at Austin. He   then worked as a postdoc at Carnegie Mellon University. He joined USTC since   2020. His research interest is unraveling the intertwined relation between   the topological and geometrical properties, and various degrees of freedom   such as charge, valley, spin, and lattice, through nonlinear transport and   nonlinear optical phenomena.