arXiv subjects

Yayi Lin

Publications and source records attributed to Yayi Lin.

4 recordsLinked to original sources

arXiv2026

Contactless terahertz mapping of wafer-scale superconducting NbTiN thin films

For large-scale superconducting quantum technology, e.g. quantum computing, the homogeneity of wafer-scale superconducting thin films is vital for consistent performance of the fabricated devices. Terahertz (THz) spectroscopy as a contactless and non-destructive measurement technique is a powerful tool to characterize the superconducting films. In this work, a set of niobium titanium nitride (NbTiN) thin films on 4-inch and 6-inch silicon wafers, grown via plasma-enhanced magnetron sputtering, are investigated via THz spectroscopy: full wafers are mapped at room temperatures and exemplary segments are characterized at cryogenic temperatures. The deviations in observed sheet resistance depend on the used deposition device and the film thickness. While the deviations in superconducting sheet kinetic inductance match those of the normal-state sheet resistance, the critical temperature and energy gap exhibit little variation. This THz mapping technique demonstrates the feasibility of evaluating wafer-scale superconducting thin films before lithography, facilitating preparation of the thin films for reproducible device fabrication.

cond-mat.supr-con↗

arXiv2026

Signatures of Dynes superconductivity in the THz response of ALD-grown NbN thin films

The frequency-dependent complex optical conductivity reflects key properties of superconductors, such as the energy gap in the density of states (DOS) and the superfluid density. For disordered superconductors, the optical conductivity often can be described within Bardeen-Cooper-Schrieffer (BCS) theory, while in corresponding tunneling experiments, deviations in the observed DOS typically require modelling by the phenomenological Dynes formula. The implications of such Dynes DOS for optics were rarely discussed so far. Here we probe the terahertz conductivity of superconducting NbN thin films with thicknesses ranging from 4.5 to 20nm, which were grown by atomic layer deposition (ALD). Our frequency range from 0.3 to 2.1 THz covers energies below and above the spectral gap. For 20nm thick NbN, we find in the optical conductivity distinct deviations from the BCS model, including a step-like characteristic in the absorption at half the zero-temperature spectral gap. These observations can be fully captured by Dynes electrodynamics with a small and temperature-independent pair-breaking rate. For the other films, we also observe signs of Dynes electrodynamics, and we discuss the evolution of the energy gap, the superfluid density, and the pair-breaking rate as function of film thickness.

cond-mat.supr-con↗

arXiv2025

THz electrodynamics and superconducting energy scales of ZrN thin films

The terahertz (THz) properties of ZrN thin films grown with CMOS-techniques on industry-standard 300 mm silicon wafers are investigated in order to explore their superconducting behavior. The films have thicknesses ranging from 18 to 48 nm, and their critical temperatures Tc are between 5 and 7.3 K. We probe the real and imaginary parts of the complex dynamical conductivity sigma in the frequency range from 100 - 540 GHz (0.4 - 2.2 meV) and as a function of temperature. The experiments provide direct access to the low-energy electrodynamics and key materials parameters such as superconducting energy gap and superfluid density. Our findings indicate that ZrN is a weakly coupled BCS-type superconductor with a gap-to-Tc ratio of approximately 3.4 in the thick film limit. For thinner films, this coupling ratio increases up to 4.0, departing from the BCS prediction. The results establish large-scale ZrN thin films as promising material for high-frequency superconducting applications.

cond-mat.supr-con↗

arXiv2022

Terahertz Receiver based on Room-Temperature Rydberg-Atoms

Realization of practical terahertz wireless communications still faces many challenges. The receiver with high sensitivity is important for THz wireless communications. Here we demonstrate a terahertz receiver based on the cesium Rydberg atoms in a room-temperature vapor cell. The minimum detectable THz electric field is calibrated. With this receiver, the phase-sensitive conversion of amplitude-modulated or frequency-modulated terahertz waves into optical signals is performed. The results show that the atomic receiver has many advantages due to its quantum properties. Especially, the long distance THz wireless communications is achievable using this receiver. Furthermore, the atomic receiver can be used in the THz wireless-to-optical link.

physics.atom-ph↗