In our most recent work, in collaboration with the Wu lab at Princeton and the Rappe group at Penn, we have demonstrated that we can use mechanical force to write nanoscale superconducting lines onto a surface. We used an atomic force microscope to apply stress under its tip on MoTe2 stacks that were built on a patterned palladium substrate. The applied stress then drives the chemical reaction that forms a Pd7MoTe2 nanowire, which is ten atomic layers thick and acts as a superconductor at low temperature. Since the stress supplies the reaction energy that is normally provided by heat, this process runs near room temperature, without the need to go to high temperatures (ca. 200 °C). We can make this superconductor exactly where we want it, with features as narrow as about 50 nm. Our collaborators in the Rappe group have done first principles calculations to explain this: the compression under the AFM tip lowers the reaction barrier and helps palladium chemisorb onto the tensile strained MoTe2.
The result is a nice demonstration of what mechanochemistry can do for quantum materials. Instead of heating a whole sample and hoping the right phase forms in the right place, we can draw arbitrary patterns of a functional 2D material with a tool that is already common in nanoscale labs. The work was led by former postdoc Shuai Zhang, and it points toward a route for building nanoscale superconducting circuits and other quantum devices by writing them mechanically.
Read the full paper: S. Zhang et al., “Mechanochemical Nano-Writing of an Atomically Thin Metal,” Physical Review X (2026). DOI: https://doi.org/10.1103/g2rj-jt2f
Penn Engineering feature: Scientists Use Force to Write Atomically Thin Superconductors