Sophie Weber
The importance of solid-state surfaces has long been recognized in the field of semiconductor devices: the discontinuity in electrostatic potential at a surface enables useful properties such as rectification and gain. Less recognized is the fact that a surface lowers the bulk symmetry of a material in exactly the same way as an applied electric field. This has the profound consequence that any quantity that can be induced by an applied electric field in bulk can exist without an external field at a surface due to the surface's intrinsic field. I have been involved in recent work applying this general bulk-boundary correspondence to the case of bulk magnetoelectric (ME) effects, whereby an applied electric field induces a net magnetization in the bulk. I will first show our results, based on symmetry analysis and first-principles density functional theory, revealing how ME effects in the bulk allow us to predict equilibrium magnetic order at a surface [1-3]. I will then discuss the case of materials with high-order bulk ME effects (where the induced magnetic is quadratic or cubic in the applied field strength), which in addition to an equilibrium surface magnetization, also have a linear surface ME effect when an electric field is applied [4]. Finally, I will touch on some promising features of surface magnetization and surface ME effects for low-dissipation spintronics applications, and discuss their relevance for van der Waals materials in particular.
1. S. F. Weber et al., Phys. Rev. X 14, 021033 (2024)
2. O. V. Pylypovskyi, S. F. Weber et al., Phys. Rev. Lett. 132, 226702 (2024)
3. S. F. Weber et al., arXiv:2412.06625 (2024)
4. S. Bhowal,... S. F. Weber..et al., arXiv:2411.12434 (2024)