Novel circuit design for high-impedance and non-local electrical measurements of two-dimensional materials

TL;DR

This paper introduces an optical isolator circuit that improves electrical measurements of high-impedance states in two-dimensional materials, enabling more accurate characterization crucial for quantum technology development.

Contribution

The paper presents a novel optical isolator circuit that decouples current injection from voltage sensing, enhancing measurement accuracy of 2D materials' electrical properties.

Findings

Successfully benchmarked with graphene non-local resistance measurements.

Accurately characterized WS2 transistor transfer characteristics.

Demonstrated potential for rapid analysis of insulating states.

Abstract

Two-dimensional materials offer a novel platform for the development of future quantum technologies. However, the electrical characterisation of topological insulating states, non-local resistance and bandgap tuning in atomically-thin materials, can be strongly affected by spurious signals arising from the measuring electronics. Common-mode voltages, dielectric leakage in the coaxial cables and the limited input impedance of alternate-current amplifiers can mask the true nature of such high-impedance states. Here, we present an optical isolator circuit which grants access to such states by electrically decoupling the current-injection from the voltage-sensing circuitry. We benchmark our apparatus against two state-of-the-art measurements: the non-local resistance of a graphene Hall bar and the transfer characteristic of a WS2 field-effect transistor. Our system allows the quick characterisation of novel insulating states in two-dimensional materials with potential applications in future quantum technologies.