概要

Atomically thin van der waals materials, such as graphene, possess a unique ability to precisely control a wide range of parameters—such as stacking with dissimilar materials and gate-voltage tunability—making them one of the ideal model systems for research in condensed-matter physics. However, owing to their extremely small volume, available measurement techniques are limited, and previous studies have largely focused on electrical transport and visible-light optical measurements. In some systems, however, electrical resistance is not necessarily an information-rich physical quantity. For example, in superconductors the resistance becomes zero regardless of microscopic details, while in insulators the resistance is often too large to be measured reliably.

For superconductors, inductance, and for insulators, capacitance (dielectric permittivity), remain finite physical quantities that directly reflect intraband electronic responses. Nevertheless, these properties have either been difficult to measure in atomically thin materials or have not received sufficient attention to date.

In this talk, I present our recent studies on inductance and capacitance measurements in atomically thin materials and provide an overview of emerging measurement methodologies for nanomaterials. Specifically, for superconductors, we have developed an inductance measurement technique applicable to samples only a few atomic layers thick, and we report the first direct observation of an enhancement of superfluid stiffness arising from quantum-geometric effects in twisted bilayer graphene. For insulating systems, we introduce quantitative evaluations of magnetoelectric coupling based on the dielectric response of atomically thin multiferroic materials, as well as observations of magnetic dynamics in atomically thin magnets using high-frequency measurements.