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arXiv · 2505.22198

Solvated electrons in polar liquids as epsilon-near-zero materials tunable in the terahertz frequency range

Matthias Runge·Michael Woerner·Denys I. Bondar·Thomas Elsaesser
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Abstract

Electrons in polar liquids give rise to a polaron resonance at a terahertz (THz) frequency \nu_0 depending on electron concentration. The impact of this resonance on light propagation is studied in experiments, where a femtosecond pump pulse generates electrons via multiphoton ionization and a THz probe pulse propagated through the excited sample is detected in a phase-resolved way. We observe a behavior characteristic for epsilon-near-zero (ENZ) materials with strongly modified phase and group velocities around \nu_0, and a broadening of the THz pulse envelope below \nu_0. Calculations based on a local-field approach reproduce the ENZ behavior.

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Matthias Runge, Michael Woerner, Denys I. Bondar, Thomas Elsaesser. 2025-05-28. Solvated electrons in polar liquids as epsilon-near-zero materials tunable in the terahertz frequency range. https://doi.org/10.1103/physrevlett.134.056901

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