Technological advances are increasingly dependent on the development of new materials, often requiring a deep understanding of their physical properties at the nanoscale. Traditional measurements of bulk or non-local quantities alone are insufficient. A new generation of instruments must be developed that can probe materials properties at nanometer length scales. However, at these scales, the strength of signals (e.g., electric, magnetic, or thermal) from these tiny regions is weak, so these instruments must also be extremely sensitive. This project supports development of a cryogenic scanning probe microscope based on a non-invasive superconducting quantum interference device (SQUID) sensor with ultra-high sensitivity to both magnetic and thermal properties. The specific nanoSQUID technology employed in this instrument, a SQUID at the tip of a nano-pipette, has application to a broad range of systems. The instrument enables materials research in superconductivity, nanomagnetism, spintronics, quantum information and computing, topological materials, and quantized thermal transport and dissipation mechanisms. The multi-function scanning probe microscope is developed through an interdisciplinary collaboration of faculty, staff, and students at the Denver and Boulder campuses of the University of Colorado. Its development trains a full-time graduate student and three undergraduate students in instrumentation, cryogenics, and multiple other physics and engineering topics under the mentorship of two senior faculty and two senior engineering staff with complementary areas of expertise. This instrument is part of a suite of nanospectroscopy tools in the Colorado Front Range that brings in a diverse user base of academics, national laboratory scientists, and industry members from the local area and across the country.
This project develops a low-temperature (300 mK) scanning probe microscope incorporating a SQUID sensor on the tip of a nanoscale quartz pipette that meets a critical need in the understanding of local magnetic and thermal material properties. This "SQUID-on-Tip" operates as magnetometer, susceptometer, and thermometer with spatial resolution as good as 50 nm, single-electron-spin magnetic sensitivity, and micro-Kelvin thermal sensitivity, orders of magnitude beyond the thermal sensitivity of other probes. The combination of these capabilities in one instrument enables many studies that cannot be carried out by any other instrument. Research projects enabled by this new instrument include studies of topological superconductors, Majorana fermions, topologically protected magnetic solitons as well as novel quantum switches, artificially engineered thermoelectrics, studies of quantized thermal transport, and more. This project is developmental because no comparable instrument is available commercially. The project scope is to implement the fabrication technology of the SQUID-on-Tip sensor and to incorporate the sensor in an ultra-low-temperature scanning probe microscope utilizing a dry low-temperature cryostat. Fabrication of the sensor requires a novel vacuum deposition system that allows for thermal evaporation of a superconducting film on a cryogenically cooled quartz nano-pipette. The scanning probe microscope integrates commercial positioning stages with the SQUID-on-Tip sensor and associated electronics. The project scope includes a commissioning phase using magnetic or superconducting meanders, or magnetic vortices for microscope verification. The goal of this project is to provide collaborative access to this multi-function instrument to a diverse user base from academia, national laboratories, and industry.
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.
