Tuning of Two-Dimensional Plasmon–Exciton Coupling in Full Parameter Space: A Polaritonic Non-Hermitian System

• DOI: 10.1021/acs.nanolett.1c00198
• Publication Date: 2021-03-09T22:28:36Z
• Authors: Yungang Sang; Chun-Yuan Wang; Soniya S. Raja; Chang-Wei Cheng; Chiao-Tzu Huang; Chun-An Chen; Xin-Quan Zhang; Hyeyoung Ahn; Chih-Kang Shih; Yi-Hsien Lee; Jinwei Shi; Shangjr Gwo
• Keywords: 02 engineering and technology; 0210 nano-technology

Non-Hermitian photonic systems with gains and/or losses have recently emerged as a powerful approach for topology-protected optical transport and novel device applications. To date, most of these systems employ coupled optical systems of diffraction-limited dielectric waveguides or microcavities, which exchange energy spatially or temporally. Here, we introduce a diffraction-unlimited approach using a plasmon-exciton coupling (polariton) system with tunable plasmonic resonance (energy and line width) and coupling strength. By designing a chirped silver nanogroove cavity array and coupling a single tungsten disulfide monolayer with a large contrast in resonance line width, we show the tuning capability through energy level anticrossing and plasmon-exciton hybridization (line width crossover), as well as spontaneous symmetry breaking across the exceptional point at zero detuning. This two-dimensional hybrid material system can be applied as a scalable and integratable platform for non-Hermitian photonics, featuring seamless integration of two-dimensional materials, broadband tuning, and operation at room temperature.