Fluxoid-based digitized mechanical torque in subfemtonewton-meter range

Abstract

A technique is proposed that realizes fluxoid-based mechanical torque in the subfemtonewton-meter range. By exploiting the fluxoid quantization of a superconductor ring, one can generate discrete torque steps in constant interval. The interval of the torque steps is estimated be 0.40 fN m for a 50-nm-thick Nb-film ring of diameter 21 mu m with a hole of diameter 7 mu m under field 0.02 T applied parallel to the ring plane. Working principles and numerical estimation are discussed by using a model system composed of a microbridge torsion lever loaded with a superconducting quantum interference device. (C) 2011 American Institute of Physics. [doi:10.1063/1.3531556]