Experiment of the Century: Fabrication and Measurement of the Bimetallic Superconducting Loop with an Andreev Interferometer

Abstract

The experiment tomeasure the thermoelectric effect in a superconducting bimetallic loop was realised using an integrated mesoscopic circuit with an Andreev interferometer as readout. The aim was to apply nanofabrication technologies to this unsolved problem in physics. An additional goal was to examine the interaction between two bimetallic loops. The Andreev interferometer had a normal resistance of RN = 5.6 kΩ. The maximum resistance modulation was 35.6%. The interferometer displayed a quantized resistance close to the Sharvin resistance. Both the high modulation and the quantization are unexpected results. To measure the thermoelectric effect, part of the loop was heated. Quasiparticles were injected through the Josephson junctions into the loop. Anon-trivial effectwas observed in the readout. With increasing current, the resistance decreased. In the loop interaction experiments, a part of the loop not connected to the readout was heated. The results from the loop interaction experiments are inconclusive. We recommend that more samples are fabricated in order to repeat the result. The observed results should be explained theoretically as soon as possible. In future experiments, the induced temperature gradients must be measured.