High-precision resistance ratio measurements by means of a novel Josephson potentiometer

Abstract

Non-decadic resistance ratios can be determined with high accuracy by means of a novel Josephson potentiometer. The advantage of this potentiometric method has been demonstrated by the first measurements of the resistance ratio 12.9 kΩ. to 10 kΩ of the quantized Hall resistance, step i = 2, of a GaAs-Ga <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1−x</inf> Al <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> As-heterostructure and a 10-kΩ cryogenic resistor. The limitation of the described method is given by the noise voltages which are generated by the room-temperature electronic null detector. Considerable improvement is anticipated by replacing the electronic null detector by a highly sensitive superconducting quantum interference device (SQUID) instrument.