Berlin 2024 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 18: Superconductivity: Poster
TT 18.1: Poster
Montag, 18. März 2024, 15:00–18:00, Poster C
Terahertz investigations on ALD-grown superconducting NbN thin films — •Yayi Lin1, Frederik Bolle1, Martin Dressel1, Detlef Born2, Heidemarie Schmidt2, and Marc Scheffler1 — 11. Physikalisches Institut, Universität Stuttgart, Stuttgart, Germany — 2Leibniz Institute of Photonic Technology (IPHT), Jena, Germany
Niobium nitride (NbN) thin films are high-disorder superconductors, that have attracted significant interest in recent years. Due to its high critical temperature (Tc up to 17 K) and large energy gap, NbN is applied in single photon detectors, microwave resonators, and superconducting quantum circuits.
As the energy gap of NbN is located in the terahertz (THz) region (3 - 100 cm−1, 100 GHz - 3 THz), we use THz spectroscopy to directly determine the energy gap from the complex optical conductivity (σ). By measuring the THz transmission, σ can be derived, which encodes various superconducting properties of NbN.
Here, we measured NbN grown by atomic layer deposition (ALD) with the nominal thicknesses of 4.5, 5.0, 10.0, and 20.0 nm on Al2O3 substrates, in both THz frequency-domain spectroscopy (THz-FDS; frequencies 3 - 40 cm−1) and THz time-domain spectroscopy (THz-TDS; 10 - 100 cm−1), at temperatures down to 2.7 K, revealing Tc, the complex optical conductivity, energy gap, and superfluid density.
Keywords: disordered superconductors; NbN; THz frequency-domain spectroscopy; THz time-domain spectroscopy; optical conductivity