On-chip time-domain terahertz spectroscopy of superconducting films below the diffraction limit

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 GHz to 750 GHz. We measure the optical conductivity of a 7.5-$\mu$m 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.

References in corpus (5)

• Electrodynamics of Correlated Electron Materials
• Moiré heterostructures as a condensed matter quantum simulator
• Ultrafast helicity control of surface currents in topological insulators with near-unity fidelity
• On-chip terahertz modulation and emission with integrated graphene junctions
• Nonlinear transport in a photo-induced superconductor

Cited by in corpus (1)

• Room-Temperature Plasmon-Assisted Resonant THz Detection in Single-layer Graphene Transistors