Fig. 1: PbI2 crystal structure, vibrational response, and dielectric properties in the THz range. | Nature Communications

Fig. 1: PbI2 crystal structure, vibrational response, and dielectric properties in the THz range.

From: High quality-factor terahertz phonon-polaritons in layered lead iodide

Fig. 1: PbI2 crystal structure, vibrational response, and dielectric properties in the THz range.The alternative text for this image may have been generated using AI.

a Monolayer (ML) arrangement of the atomic lattices of PbI2 with top and side views of its unit cell. b Overview of its real part of the permittivity and delimitation of hyperbolic, surface, and Reststrahlen bands. Ranges for the Reststrahlen bands type I (RB-1) and type II (RB-2) are indicated. c Detailed view of the permittivity in the range between 95 and 120 cm−1 comprising hyperbolic and surface phonon-polaritons (SPhP). d Raman spectrum of PbI2 flakes with indication of the active modes. e Far-field THz Time-Domain Spectroscopy (TDS) absorption spectrum of an isolated PbI2 crystal fitted by a phenomenological model (Supplementary Information, Section 7). f Optical microscopy image of the PbI2 crystals transferred to a Si substrate. g Zoomed optical image with fine details of the 2D crystals (area within the white dashed square in f). Scale bars in (f, g) represent 50 and 10 μm, respectively.

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