On-Chip Time-Domain Terahertz Spectroscopy of Superconducting Films below the Diffraction Limit.
basic_science · Level V
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- Record sourced from PubMed, PMID 37126575.
- Also identified by DOI 10.1021/acs.nanolett.3c00412.
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Abstract
Free-space time domain THz spectroscopy accesses electrodynamic responses in a frequency regime ideally matched to interacting condensed matter systems. However, THz spectroscopy is challenging when samples are physically smaller than the diffraction limit of ∼0.5 mm, as is typical, for example, in van der Waals materials and heterostructures. Here, we present an on-chip, time-domain THz spectrometer based on semiconducting photoconductive switches with a bandwidth of 200 to 750 GHz. We measure the optical conductivity of a 7.5-μm wide NbN film across the superconducting transition, demonstrating spectroscopic signatures of the superconducting gap in a sample smaller than 2% of the Rayleigh diffraction limit. Our spectrometer features an interchangeable sample architecture, making it ideal for probing superconductivity, magnetism, and charge order in strongly correlated van der Waals materials.