CMP Seminar by Emil Viñas Boström

Title: Merging condensed matter and quantum optics - Cavity quantum electrodynamics with magnetoelectric materials

Speaker: Emil Viñas Boström, Max Planck Institute for the Structure and Dynamics of Matter, Hamburg 

Abstract: Chirality is a fundamental feature of the natural world, which in solids typically emerges from a loss of improper rotation axes due to asymmetric atomic coordinates. Beyond such structural chirality, other forms can exist in solids with achiral lattices, generated by instabilities such as ferroaxial orders and helical magnetic textures. The latter are gaining attention because of their ability to drive macroscopic ferroelectric polarizations intertwined with the magnetic order, and for their relevance to a wide range of next-generation technological applications. Materials with such intertwined magnetic and electric orders are known as type-II multiferroics, or magnetoelectric materials. 

In this talk, I will discuss how magnetoelectric materials can be utilizied for cavity vacuum engineering, where vacuum fluctuations of the electromagnetic field interacts with and modifies properties of an adjacent material. In particular, I will show how the interface between vacuum and a magnetoelectric material will as a surface cavity [1], where the surface modes arise from electromagnons. The unconventional properties of these surface modes make it possible to imprint time-reversal symmetry breaking and chirality in the photon field, such that it can affect an adjacent materials. This is exemplified for the case of single-layer graphene, where the interaction with magnetoelectric surface fluctuations open a topological gap. The resulting cavity-induced state carries an integer Chern number but a finite anyon angle, signaling an intruiging mixture of single-particle (integer quantum Hall) and many-particle (fractional quantum Hall) phenomena.

I will also discuss some ongoing and future ideas to read and write correlations of materials using methods of quantum optics.
 

Refs.
[1] Anyonic Chern insulator in graphene induced by surface electromagnon vacuum fluctuations. Xinle Cheng, Emil Viñas Boström, Frank Y. Gao, Edoardo Baldini, Dante M. Kennes and and Angel Rubio. arXiv:2511.10836