Hall signal-dominated microwave transmission through graphene-loaded waveguides

TL;DR

This study uses microwave transmission spectroscopy to observe the quantum Hall effect in graphene, revealing how sample geometry influences signal sensitivity and demonstrating a resistive circuit model to explain these effects.

Contribution

It introduces a novel microwave transmission method to detect quantum Hall edge modes in graphene and shows how device geometry affects measurement sensitivity.

Findings

Plateaus in transmitted power correspond to quantum Hall edge modes.

Sample geometry significantly impacts measurement sensitivity.

A resistive circuit model explains the enhanced sensitivity in certain samples.

Abstract

Microwave transmission line spectroscopy is used to observe the integer quantum Hall effect in two samples of monolayer graphene with different geometries that are resistively-coupled to a coplanar waveguide. We find plateaus in transmitted power that do not vary significantly with microwave frequency but are significantly different for two samples due to their shape. With each drop in transmitted power corresponding to an additional quantum Hall edge mode that short the transmission line to ground, these well-known quanta of conductance allow us to calibrate the sensitivity of the devices. One sample with short contact regions matched the sensitivity expected when considering only the quantum Hall conductance of $\nu e^2/h$; another sample with long contact regions demonstrated a nearly three-fold enhancement in sensitivity. We model this result with a purely resistive circuit that introduces an additional resistance to explain the increased sensitivity.