The TRR 227 kindly invites you to a special TRR 227 Seminar.

Speaker: Prof. Dr. Liang Wu, University of Pennsylvania, USA

Title:

Novel nonlinear optical response in 2D antiferromagnets

Abstract:

The family of monolayer two-dimensional (2D) materials hosts a wide range of interesting phenomena, including superconductivity, charge density waves, topological phases and magnetism. Antiferromagnets (AFMs) have also attracted enormous interest recently in spintronics due to the absence of stray fields and their terahertz resonant frequency. Despite the great advantages of antiferromagnetic spintronics, controlling and directly detecting antiferromagnetic order and other emergent order in 2D materials have been challenging.

In my talk, I will focus on the Neel order in 2D AFMs (MnPS₃ and MnPSe₃). I will show that we have developed a sensitive second-harmonic generation (SHG) microscope and detected long-range Neel antiferromagnetic (AFM) order down to the monolayer in MnPSe₃ [1] and the bilayer in MnPS₃ [2]. In MnPSe₃, we observed the switching of an Ising-type Neel vector reversed by the time-reversal operation. We rotated them by an arbitrary angle irrespective of the lattice by applying uniaxial strain. Finally, I will also talk about novel nonlinear optical response of MnPSe₃ and MnPS₃ to external fields such as spatially variant strain and magnetic field [3,4].

[1] Ni et al. Nature Nanotechnol. 16, 782-787 (2021)
[2] Ni et al. Phys. Rev. Lett. 127, 187201 (2021)
[3] Ni et al. arXiv:2404.06010
[4] Ni et al. under review