Quantum Microscopy with a van der Waals Quantum Sensor

Microscopes based on solid-state quantum sensors have recently emerged as powerful tools for probing material properties and physical processes in regimes not accessible to classical sensors, especially on the nanoscale [1]. Quantum microscopy has been used to image a variety of phenomena, from magnetism and charge transport in nanoscale devices to remanent magnetic fields from ancient rocks and biological organisms [1-3]. However, applications of these microscopes have so far mainly relied on spin defects hosted in a rigid, three-dimensional crystal which limits their ability to closely interact with the sample under study. In this context, a long-standing goal has been to identify a spin defect in a two-dimensional van der Waals (vdW) material suitable for quantum microscopy. In this work [4], we demonstrate a versatile and robust quantum microscope using spin defects embedded within a vdW material, hexagonal boron nitride (hBN) [5]. To showcase the multi-modal capabilities of this platform, we assemble vdW heterostructures incorporating a quantum-active hBN layer, and demonstrate simultaneous temperature and magnetic imaging of a vdW ferromagnet, as well as of an operating graphene device. By enabling intimate proximity between sensor and sample, potentially down to a single atomic layer, the hBN quantum sensor opens new frontiers for nanoscale quantum sensing and microscopy. Moreover, given the ubiquitous use of hBN in modern materials and condensed matter physics research, the technique is well-placed to find widespread use in these fields. Preliminary results also showcase the potential for the use of more advanced quantum sensing protocols to sense fluctuating signals, with applications in the physical and life sciences envisaged. <br/><br/>[1] F. Casola, et al <i>Nat. Rev. Mater. </i><b>3</b>, 17088 (2018)<br/>[2] L. Thiel, et al <i>Science</i> <b>364</b>, 973-976 (2019)<br/>[3] M. J. Ku, et al <i>Nature </i><b>583</b>, 537-541 (2020)<br/>[4] A. Healey, at al arXiv:2112.03488 (2021)<br/>[5] A. Gottscholl, et al <i>Nature Materials </i><b>19</b>, 540 (2020)