MRI: Development of a Scanning 4-Probe Microscope for Discovery and Characterization of Quantum Materials and Devices

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Non-Technical DescriptionA key challenge in quantum technology development is to understand the link between the atomic-scale building blocks or "quanta" of materials (the charges and spins of electrons) and the motion of these building blocks that give a device its function. This project supports development of a novel 4-probe microscope to address this challenge. The new microscope independently scans four switchable probes across a material or device: individual probes can image static atoms, charges, and spins, while two or more probes together can detect the motion of these charges and spins from 10s of nanometers to 100s of micrometers in length. The microscope also operates in a high magnetic field and with samples cooled to liquid helium temperature - thus allowing access to a new regime of quantum phenomena. Projects enabled by this microscope include screening of new inhomogeneous materials, mapping the flow of electrons around single atom defects, developing nanostructured materials such as braided polymer cables, assembling complex sensors from individual atoms, and searching for emergent particles that can become the building blocks of new technologies. The microscope development is carried out in collaboration between Harvard and a small company; graduate students and postdoctoral researchers are trained through the microscope development process and later, in pursuing the launch of a commercial product. The microscope is housed in Harvard's Center for Nanoscale Systems, a scientific nexus for many Northeast colleges, universities, and industries. The microscope's dedicated staff provides technical education to an intellectually and demographically diverse cadre of users, and in turn serves as a point of connection and inspiration for cross-disciplinary ideas.Technical DescriptionThis Major Research Instrumentation grant supports development of a compact and versatile scanning 4-probe microscope (S4PM), to facilitate the discovery and fabrication of novel quantum materials and devices. The S4PM meets a critical need to understand the relationship between the static atomic structure and electronic wave functions of a material at the sub-Angstrom scale, and the electrical and magnetic transport properties across 10s of nanometers to 100s of microns that lead to device functionality. The S4PM employs a novel rotary motion design that reduces instrument size and allows operation at about 1 Kelvin, up to 5 Tesla of magnetic field, and 10s of nanometer transport resolution. The S4PM allows flexible in-situ exchange of a wide variety of complementary probes including scanning tunneling microscopy, atomic force microscopy, scanning gate, and scanning diamond nitrogen-vacancy. Research projects enabled by this S4PM include screening the transport properties of inhomogeneous new materials, mapping electron and spin flow around single atom defects and constrictions, developing nanostructured materials such as braided polymer Litz cables, assembling atomic-scale sensors such as a very small superconducting quantum interference device, and searching for emergent particles such as Majorana fermions and magnetic monopoles.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.