Terahertz chiral photonic-crystal cavities for Dirac gap engineering in graphene

TL;DR

This paper designs high-quality terahertz chiral photonic-crystal cavities with broken time-reversal symmetry, enabling enhanced light-matter interactions and the potential to induce topological phases in graphene.

Contribution

It introduces a novel design for THz chiral photonic-crystal cavities using magnetoplasma, incorporating ab initio calculations to estimate cavity-induced gaps in graphene.

Findings

Achieves broken TRS in THz cavities using magnetoplasma.

Predicts a cavity-induced energy gap of about 1 meV in graphene.

Demonstrates enhanced light-matter interaction due to Dirac nodes.

Abstract

Strong coupling between matter and vacuum electromagnetic fields in a cavity can induce novel quantum phases in thermal equilibrium via symmetry breaking. Particularly intriguing is the coupling with circularly polarized cavity fields, which can break time-reversal symmetry (TRS) and lead to topological bands. This has spurred significant interest in developing chiral cavities that feature broken TRS, especially in the terahertz (THz) frequency range, where various large-oscillator-strength resonances exist. Here, we present a design for high-quality-factor THz chiral photonic-crystal cavities (PCCs) that achieves broken TRS using a magnetoplasma in a lightly doped semiconductor. We incorporate ab initio density functional theory calculations into the derived microscopic model, allowing a realistic estimate of the vacuum-induced gap in graphene when coupled to our chiral cavity. Our calculations show an enhancement in the light-matter interaction due to Dirac nodes and predict an energy gap on the order of 1 meV. The THz chiral PCCs offer a promising platform for exploring cavity-dressed condensed matter with broken TRS.