Cavity Quantum Electrodynamics with Hyperbolic van der Waals Materials

Yuto Ashida, Atac Imamoglu, Eugene Demler

Published 2023-01-09Version 1

The ground-state properties and excitation energies of a quantum emitter can be modified in the ultrastrong coupling regime of cavity quantum electrodynamics (QED) where the light-matter interaction strength becomes comparable to the cavity resonance frequency. Recent studies have started to explore the possibility to control an electronic material by embedding it in a cavity that confines electromagnetic fields in deep subwavelength scales. Currently, there is a strong motivation to realize ultrastrong-coupling cavity QED in the terahertz (THz) range, since most of the elementary excitations of quantum materials are in this frequency window. We propose and analyze an ideal platform to achieve this aim where a two-dimensional electronic material is encapsulated by a planar cavity consisting of ultrathin polar van der Waals crystals. As a concrete setup, we show that nanometer-thick hexagonal boron nitride layers allow for reaching the ultrastrong coupling regime for single-electron cyclotron resonance in a bilayer graphene. The proposed cavity setting can be realized by a wide variety of thin dielectric materials with hyperbolic dispersions. Consequently, van der Waals heterostructures could provide an ideal playground for exploring the ultrastrong-coupling physics of cavity QED materials.