Strong magnetoresistance in a graphene Corbino disk at low magnetic fields

TL;DR

This study measures low-field magnetoresistance in suspended graphene Corbino disks, revealing a strong quadratic dependence at the Dirac point and insights into scattering mechanisms and impurity screening, with potential for sensitive magnetic detection.

Contribution

It provides the first detailed characterization of low-field magnetoresistance in suspended graphene Corbino devices, highlighting the effects of charge density, scattering, and impurity screening.

Findings

Magnetoresistance reaches 4000 B^2% at the Dirac point.

Magnetoresistance decreases by a factor of two with increased charge density.

Device exhibits a magnetic field sensitivity of 60 nT/√Hz.

Abstract

We have measured magnetoresistance of suspended graphene in the Corbino geometry at magnetic fields up to $B=0.15\,$T, i.e., in a regime uninfluenced by Shubnikov-de Haas oscillations. The low-temperature relative magnetotoresistance $[R(B)-R(0)]/R(0)$ amounts to $4000 B^2\% $ at the Dirac point ($B$ in Tesla), with a quite weak temperature dependence below $30\,$K. A decrease in the relative magnetoresistance by a factor of two is found when charge carrier density is increased to $|n| \simeq 3 \times 10^{-10}$ cm$^{-2}$. The gate dependence of the magnetoresistance allows us to characterize the role of scattering on long-range (Coulomb impurities, ripples) and short-range potential, as well as to separate the bulk resistance from the contact one. Furthermore, we find a shift in the position of the charge neutrality point with increasing magnetic field, which suggests that magnetic field changes the screening of Coulomb impurities around the Dirac point. The current noise of our device amounts to $10^{-23}$ A$^2$/$\sqrt{\textrm{Hz}}$ at $1\,$kHz at $4\,$K, which corresponds to a magnetic field sensitivity of $60$ nT/$\sqrt{\textrm{Hz}}$ in a background field of $0.15\,$T.