Physikalische Chemie - Direktor: Prof. Dr. Martin Wolf
Host: Alex Paarmann
Monday, June 19, 2023, 11:00 am
All are invited to meet around 10:40 am for a chat with coffee & cookies.
PC Seminar Room, G 2.06, Faradayweg 4
Penn State University
Semiconductors and Topological Insulators for Infrared and Terahertz Metamaterials
When working in the infrared (IR) or terahertz (THz) spectral ranges, traditional optical materials like gold and silver have extremely large and negative permittivities. This means it is difficult to use these materials for plasmonics or hyperbolic metamaterials, both of which require materials with relatively small and negative permittivities. We must therefore explore alternative materials. In this talk, I will focus on two classes of materials: heavily-doped III-V semiconductors for the IR and topological insulators for the THz. I will first discuss our work on using heavily-doped III-V semiconductors as tunable IR plasmonic materials as well as components in layered hyperbolic metamaterials (HMMs). I will show data demonstrating that our layered HMMs show negative refraction as well as strong coupling to embedded quantum wells. Topological insulators (TIs) are materials that have a bulk band gap crossed by surface states with linear dispersion. These surface states are present at the physical boundaries of the material, and host two-dimensional, massless electrons that are spin-momentum locked. When they couple to a photon, these electrons form the basis of Dirac plasmon polaritons (DPPs) with resonances in the THz spectral range. I will show our results demonstrating the excitation of DPPs in TIs as well as the creation of layered structure showing large effective indices that act as THz Dirac metamaterials.