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O: Fachverband Oberflächenphysik

O 100: Mini-Symposium: Infrared nano-optics II

O 100.1: Paper discussion

Donnerstag, 4. März 2021, 13:30–14:15, R2

Broad spectral tuning of ultra-low-loss polaritons in a van der Waals crystal by intercalation — •Pablo Alonso-González — University of Oviedo

Phonon polaritons (PhPs) -light coupled to lattice vibrations- hold great promises for an unprecedented control of the flow of energy at the nanoscale because of their strong field confinement and long propagation. Moreover, recent experiments in polar van der Waals (vdW) crystals such as h-BN and alfa-MoO3, have demonstrated PhPs with anisotropic propagation, and ultra-long lifetime in the picosecond range. However, a main drawback of these PhPs is the lack of tunability of the narrow and material-specific spectral range where they exist (the so-called Reststrahlen Band (RB)), which severely limits their implementation in nanophotonics technologies. Here, we demonstrate that intercalation allows for a broad spectral shift of RBs in a vdW crystal, and that the PhPs excited within them show ultralow losses (lifetime of 5 ps) similar to PhPs in the non-intercalated crystal (lifetime of 8 ps). As a difference to previous attempts, which fail in keeping the polaritonic activity of the intercalated compound, our results are possible by employing an intercalation method based on single crystal growth, that we carried out in the vdW semiconductor alfa-V2O5, thereby also adding a new member to the library of vdW materials supporting PhPs. We expect this intercalation method to be applied in other vdW materials, opening the door for the use of PhPs in broad spectral bands that eventually cover the whole mid-IR range, which seems to be elusive with currently known polaritonic materials.

Paper discussion with expert panel members

Prof. S. Law (U Delaware), Prof. M. Raschke (JILA, UC Boulder), Prof. Y. Abate (U Georgia) and L. Wehmeier (TU Dresden)