Response regimes in on-chip THz spectroscopy
Abstract
On-chip THz spectroscopy enables quantitative measurements of the optical conductivity of sub-wavelength 2D materials by tightly confining THz fields in metallic transmission line structures interfaced to the material. However, because the probed structures are smaller than the THz wavelength, finite-size and environmental effects can strongly influence the measured response. Here, we identify the conditions under which a metallic sample exhibits a genuine Drude response and when finite-size and environmental effects must be considered. We further introduce and characterize an additional regime, the Phantom-Drude response, which mimics Drude behavior but instead originates from the superposition of multiple finite-momentum plasmonic resonances. If unrecognized, this regime can lead to misinterpretation of intrinsic material properties. We systematically show how the Phantom-Drude response can emerge and demonstrate its sensitivity to sample dimensions, transmission line geometry, material shape, and gate properties, providing practical guidelines to avoid this regime in future on-chip THz measurements.
Cite
@article{arxiv.2511.23365,
title = {Response regimes in on-chip THz spectroscopy},
author = {Gunda Kipp and Marios H. Michael and Alexander M. Potts and Dorothee Herrmann and Toru Matsuyama and Guido Meier and Matthew W. Day and Hope M. Bretscher and James W. McIver},
journal= {arXiv preprint arXiv:2511.23365},
year = {2026}
}