We report a quartz crystal microbalance study of sliding friction levels in ${\mathrm{N}}_2$, ${\mathrm{H}}_2\mathrm{O}$, and superheated He films adsorbed on Pb(111) substrates alternating in and out of the superconducting state. Reductions in friction upon entry into the superconducting state are greater for ${\mathrm{N}}_2$ than He, consistent with a recent theory that linked electronic friction to adsorbate polarizability. Our work also reveals that repetitive cycling of an externally applied magnetic field may impact friction.

• Received 19 December 2005

DOI:https://doi.org/10.1103/PhysRevLett.96.226107