• Jonsson, Magnus P.
• Mohammadi, Mohsen
• Chen, Shangzhi
• Rahmanudin, Aiman
• Kim, Nara
• Duan, Yulong
• Tybrandt, Klas

Abstract

A wide range of nanophotonic applications rely on polarization-dependent plasmonic resonances, which usually requires metallic nanostructures that have anisotropic shape. This work demonstrates polarization-dependent plasmonic resonances instead by breaking symmetry via material permittivity. The study shows that molecular alignment of a conducting polymer can lead to a material with polarization-dependent plasma frequency and corresponding in-plane hyperbolic permittivity region. This result is not expected based only on anisotropic charge mobility but implies that also the effective mass of the charge carriers becomes anisotropic upon polymer alignment. This unique feature is used to demonstrate circularly symmetric nanoantennas that provide different plasmonic resonances parallel and perpendicular to the alignment direction. The nanoantennas are further tuneable via the redox state of the polymer. Importantly, polymer alignment could blueshift the plasma wavelength and resonances by several hundreds of nanometers, forming a novel approach toward reaching the ultimate goal of redox-tunable conducting polymer nanoantennas for visible light. Traditional anisotropic nanoantennas have asymmetric shape. In this work, symmetry is instead broken by straining of a conducting polymer, leading to an in-plane anisotropic plasma frequency. This enables circularly symmetric nanoantennas with polarization-dependent localized surface plasmon resonances. The polarization dependence is consistent with inverse changes of the effective mass and mobility of thecharge carriers along different in-plane directions.image ; Funding Agencies|AForsk Foundation; Knut and Alice Wallenberg Foundation; Swedish Research Council [2020-00287, 2022-00211, 2019-04424, 2020-05218]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoeping University (Faculty Grant SFO-Mat-LiU) [2009 00971]; Swedens Innovation Agency (Vinnova grant) [2021-01668]

Topics

• impedance spectroscopy
• surface
• polymer
• mobility
• anisotropic
• forming