Spatiotemporal Mapping of a Photocurrent Vortex in Monolayer MoS2 Using Diamond Quantum Sensors

Abstract

The detection of photocurrents is central to understanding and harnessing the interaction of light with matter. Although widely used, transport-based detection averages over spatial distributions and can suffer from low photocarrier collection efficiency. Here, we introduce a contact-free method to spatially resolve local photocurrent densities using a proximal quantum magnetometer. We interface monolayer MoS 2 with a near-surface ensemble of nitrogen-vacancy centers in diamond and map the generated photothermal current distribution through its magnetic field profile. By synchronizing the photoexcitation with dynamical decoupling of the sensor spin, we extend the sensor's quantum coherence and achieve sensitivities to alternating current densities as small as 20 nA/µm. Our spatiotemporal measurements reveal that the photocurrent circulates as vortices, manifesting the Nernst effect, and rises with a timescale indicative of the system's thermal properties. Our method establishes an unprecedented probe for optoelectronic phenomena, ideally suited to the emerging class of two-dimensional materials, and stimulates applications towards large-area photodetectors and stick-on sources of magnetic fields for quantum control. * Φ/ 0.5 * 8 * 2 ,

Van der Waals magnets: Wonder building blocks for two‐dimensional spintronics?

“…173 The NV spins in diamond has also enabled a new type of quantum magnetometer that reveals the spatiotemporal optoelectronic properties of monolayer semiconductor MoS 2 . 174 These techniques can be combined with other microscopy and magnetometry, such as MOKE and spin-polarized STM/STS. The latter has been employed to provide direct experimental evidence of stacking-dependent layered magnetism in MBE-grown CrBr 3 thin films.…”

“…For example, scanning single‐spin magnetometry, based on nitrogen‐vacancy (NV) center spins in diamond, has been demonstrated quite recently, and represents a powerful technique to image nanoscale magnetic domains as well as quantify the absolute magnetization of 2D‐CrI 3 flakes . The NV spins in diamond has also enabled a new type of quantum magnetometer that reveals the spatiotemporal optoelectronic properties of monolayer semiconductor MoS 2 . These techniques can be combined with other microscopy and magnetometry, such as MOKE and spin‐polarized STM/STS.…”

Diamond quantum sensors: from physics to applications on condensed matter research

“…Apart from sensing spin systems, photocurrent was also sensed by the NV centre. Zhou et al [58] investigated, using embedded NV magnetometers, the light-matter interaction through probing the photocurrent response in 2 D materials with submicron resolution. They interfaced monolayer MoS 2 with a near-surface ensemble of NV centres in diamond, and the magnetic fields measured by NV centres were mapped to the photothermal current.…”

Widefield quantum microscopy with nitrogen-vacancy centers in diamond: strengths, limitations, and prospects

“…28,29,61,62 This capability was recently used to observe the viscous Dirac fluid nature of current in graphene, 63 and to image photocurrent vortices in MoS 2 . 64 Applications in electronics also include probing currents in the microwave regime [65][66][67] and temperature mapping of electronic circuits. 19,20,68,69 The purpose of this Perspective is to analyze some of these applications in more detail and, considering the current state of the art of widefield NV microscopy, identify the strengths and shortcomings compared to other microscopy techniques typically used.…”