Near-field nanoscopy of excitons and ultrafast interlayer dynamics in van der Waals crystals

Fabian Mooshammer; Markus Plankl; Paulo E. Faria Jr.; Sanghoon Chae; Thomas Siday; Martin Zizlsperger; Fabian Sandner; Felix Schiegl; Shuai Zhang; Yinming Shao; Aaron Sternbach; Daniel J Rizzo; Simon Maier; Markus A. Huber; Martin Gmitra; Jaroslav Fabian; Jessica L. Boland; Xiaoyang Zhu; P. James Schuck; James Hone; Tyler L. Cocker; D. N Basov; Rupert Huber

doi:10.1117/12.2603471

5 March 2022 Near-field nanoscopy of excitons and ultrafast interlayer dynamics in van der Waals crystals

Fabian Mooshammer, Markus Plankl, Paulo E. Faria Jr., Sanghoon Chae, Thomas Siday, Martin Zizlsperger, Fabian Sandner, Felix Schiegl, Shuai Zhang, Yinming Shao, Aaron Sternbach, Daniel J Rizzo, Simon Maier, Markus A. Huber, Martin Gmitra, Jaroslav Fabian, Jessica L. Boland, Xiaoyang Zhu, P. James Schuck, James Hone, Tyler L. Cocker, D. N Basov, Rupert Huber

Author Affiliations +

Proceedings Volume 12009, Quantum Sensing and Nano Electronics and Photonics XVIII; 120090D (2022) https://doi.org/10.1117/12.2603471
Event: SPIE OPTO, 2022, San Francisco, California, United States

Abstract

Tip-based nanoscopy techniques have emerged as powerful tools for probing the exceptional optoelectronic properties of van der Waals crystals (vdW) on deeply sub-wavelength scales. Based on two sets of experiments, we demonstrate how bound electron–hole pairs – so-called excitons – can be interrogated with near-field microscopy. First, we build on terahertz nanoscopy with subcycle temporal resolution to access the separation of photo-carriers via interlayer tunneling and their subsequent recombination in transition metal dichalcogenide bilayers. By tracing the local polarizability of electron–hole pairs with evanescent terahertz fields, we reveal pronounced variations of the exciton dynamics on the nanoscale. This approach is uniquely suitable to reveal how ultrafast charge transfer processes shape functionalities in a variety of solid-state systems. Second, we image waveguide modes (WMs) in thin flakes of the biaxial vdW crystal ReS₂ across a wide range of near-infrared frequencies. Resolving the dependence of the WM dispersion on the crystallographic direction, polarization of the electric field and sample thickness, enables us to quantify the anisotropic dielectric tensor of ReS₂ including the elusive out-of-plane response. The excitonic absorption at ~1.5 eV induces a backbending of the dispersion and increased losses of the WMs as fully supported by numerical calculations. Thus, we provide crucial insights into the optical properties of ReS₂ and explore light-matter coupling in layered, anisotropic waveguides. Our findings set the stage for probing ultrafast dynamics in biaxial vdW crystals on the nanoscale.

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Fabian Mooshammer, Markus Plankl, Paulo E. Faria Jr., Sanghoon Chae, Thomas Siday, Martin Zizlsperger, Fabian Sandner, Felix Schiegl, Shuai Zhang, Yinming Shao, Aaron Sternbach, Daniel J Rizzo, Simon Maier, Markus A. Huber, Martin Gmitra, Jaroslav Fabian, Jessica L. Boland, Xiaoyang Zhu, P. James Schuck, James Hone, Tyler L. Cocker, D. N Basov, and Rupert Huber "Near-field nanoscopy of excitons and ultrafast interlayer dynamics in van der Waals crystals", Proc. SPIE 12009, Quantum Sensing and Nano Electronics and Photonics XVIII, 120090D (5 March 2022); https://doi.org/10.1117/12.2603471

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