Regensburg 2019 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 27: Plasmonics II (joint session O/CPP)

CPP 27.9: Vortrag

Dienstag, 2. April 2019, 16:00–16:15, H8

Low-temperature infrared dielectric function of hyperbolic α-quartz — •Christopher J. Winta, Martin Wolf, and Alexander Paarmann — Fritz-Haber-Institut der Max-Planck-Gesellschaft

Natural hyperbolic materials, where the principal components of the dielectric tensor have opposite signs, like hexagonal boron nitride [1], have recently attracted much attention due to their unique characteristics for polaritonic nanophotonics [2]. Here, we show that also the common uniaxial crystal α-quartz exhibits multiple hyperbolic bands in the far-infrared (far-IR), which support low-loss hyperbolic modes at low temperatures.

We determine the IR dielectric properties of α-quartz in the temperature range from 1.5 K to 200 K. Far-IR reflectivity spectra of a single crystal y-cut were acquired in 8 distinct configurations. Fitting a multi-oscillator model globally to these data allows for extraction of frequencies as well as damping rates of the in-plane and out-of-plane, the longitudinal and transverse IR-active optic phonon modes, and hence the temperature-dependent ordinary and extraordinary dielectric functions, ε_⊥(ω) and ε_∥(ω), respectively.

The results are consistent with previous high temperature studies [3] and indicate remarkably high quality factors, Q, for polaritons at low temperatures in α-quartz’s hyperbolic spectral region.

[1] Caldwell et al., Nature Communications 2014, 5.

[2] Liu, Lee, Xiong, Sun, Zhang, Science 2007, 315, 1686–1686.

[3] Gervais and Piriou, Phys. Rev. B 1975, 11, 3944–3950.