Imaging of Submicroampere Currents in Bilayer Graphene Using a Scanning Diamond Magnetometer

Abstract

We report on nanometer magnetic imaging of two-dimensional current flow in bilayer graphene devices at room temperature. By combining dynamical modulation of the source-drain current with ac quantum sensing of a nitrogen-vacancy center in the diamond probe tip, we acquire magnetic field and current density maps with excellent sensitivities of 4.6 nT and 20 nA/μm, respectively. The spatial resolution is 50-100 nm. We introduce a set of methods for increasing the technique's dynamic range and for mitigating undesired back-action of magnetometry operation (scanning tip, laser and microwave pulses) on the electronic transport. Finally, we show that our imaging technique is able to resolve small variations in the current flow pattern in response to changes in the background potential. Our experiments demonstrate the feasibility for detecting and imaging subtle spatial features of nanoscale transport in two-dimensional materials and conductors.

Preparation of metrological states in dipolar-interacting spin systems

“…While this study remains limited to small system sizes (N ≤ 10, limited by computational resource), our results are of immediate interest to nanoscale quantum sensing where spatial resolution is paramount and the finite sensor size limits the number of spins that can be utilized. Specific examples include the investigation of 2D materials [57][58][59][60] , structures and dynamics of magnetic domains 61,62 , vortex structures in superconductivity 63,64 , and magnetic resonance spectroscopy on individual proteins and DNA molecules [65][66][67][68] .…”

Magnetic field imaging by hBN quantum sensor nanoarray

“…21,42 Our value means that a weak field of 10 µT can be detected within one minute and 1 µT within one hour. Specifically, this performance is sufficient for addressing quantum materials such as graphene 23,[46][47][48] and vdW magnets. [22][23][24] We then demonstrate high-resolution magnetic field imaging.…”

Imaging ferroelectric domains with a single-spin scanning quantum sensor

“…The quantum phase ϕ accumulated between the two states during the coherent precession is ϕ ± = ∫ τ 0 g(t)Δω ± (t)dt, where g(t) is the modulation function 46 , Δω ± (t) = ∓2𝜋𝜋k ⟂ E ac (t) cos(2φ B + φ E ac ) sin(2𝜋𝜋ft) is the detuning (see Supplementary Section 1) and τ is the evolution time. We used a four-phase cycling technique 12,47 of the last π/2 pulse to measure ϕ ± . The readout of the NV centre's spin state was performed by another ~2 μs laser pulse, during which the photons emitted from the NV centre were collected across a ~600 ns window.…”