Extreme light confinement down to the atomic scale has been theoretically predicted for ultrathin, Ta-based transition metal dichalcogenides (TMDs). In this work, we experimentally demonstrate in 2H-TaS2 monolayers and bilayers a lateral confinement ratio up to 300 at large wave vectors of q=0.15A˚−1, and slow light behaviour with a group velocity ∼10−4c. Quantitative momentum-resolved electron energy loss spectroscopy (q-EELS) with a momentum resolution of 0.0056A˚−1 was used as a platform for the nanoscale optical measurements. With it, momentum-dispersed, two-dimensional (2D) plasmon resonances were experimentally observed, showing a transition from 2D to 3D Coulomb interaction in the high-momentum regime, equivalent to light confinement volumes of 1-2nm3. Remarkably, the resonant modes do not enter the electron-hole continuum, predicting even further enhanced optical field confinements for this material at cryogenic temperatures.
@article{arxiv.2411.07572,
title = {Slow, Nanometer Light Confinement Observed in Atomically Thin TaS2},
author = {Hue T. B. Do and Meng Zhao and Pengfei Li and Yu Wei Soh and Jagadesh Rangaraj and Bingyan Liu and Tianyu Jiang and Xinyue Zhang and Jiong Lu and Peng Song and Jinghua Teng and Michel Bosman},
journal= {arXiv preprint arXiv:2411.07572},
year = {2025}
}