Kinetic Inductance of Few-Layer NbSe$_2$ in the Two-Dimensional Limit

TL;DR

This study measures the kinetic inductance of atomically thin NbSe$_2$ superconductors, revealing layer-dependent properties and potential for quantum device applications, with a focus on the transition from clean to dirty limit behavior.

Contribution

It provides the first detailed characterization of kinetic inductance in monolayer NbSe$_2$, highlighting thickness-dependent behavior and nonlinear properties relevant for quantum technologies.

Findings

Kinetic inductance reaches 1.2 nH/□ in monolayer NbSe$_2$.

Thickness-dependent crossover from clean- to dirty-limit superconductivity.

Self-Kerr nonlinearity varies from -0.008 to -14.7 Hz/photon.

Abstract

Van der Waals (vdW) superconductors remain superconducting down to the monolayer limit, enabling the exploration of emergent physical phenomena and functionality driven by reduced dimensionality. Here, we report the characterization of the kinetic inductance of atomically thin NbSe$_2$, a two-dimensional van der Waals superconductor, using superconducting coplanar waveguides and microwave measurement techniques familiar to circuit quantum electrodynamics (cQED). The kinetic inductance scales inversely with the number of NbSe$_2$ layers, reaching 1.2 nH/$\Box$ in the monolayer limit. Furthermore, the measured kinetic inductance exhibits a thickness-dependent crossover from clean- to dirty-limit behavior, with enhanced dirty-limit contributions emerging in the ultra-thin regime. These effects are likely driven by increased surface scattering, multi-band superconductivity, and geometric confinement. Additionally, the self-Kerr nonlinearity of the NbSe$_2$ films ranges from $K/2\pi$ = -0.008 to -14.7 Hz/photon, indicating its strong potential in applications requiring compact, nearly linear, high-inductance superconducting quantum devices and detectors. The fabrication and characterization techniques demonstrated here are extensible to the investigation of other two-dimensional superconductors.