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 loopwas realised using an integrated mesoscopic circuit with an Andreev interferometer asreadout. The aim was to apply nanofabrication technologies to this unsolved problemin physics. An additional goal was to examine the interaction between two bimetallicloops.The Andreev interferometer had a normal resistance of RN = 5.6 kΩ. The maximumresistance modulation was 35.6%. The interferometer displayed a quantized resistanceclose to the Sharvin resistance. Both the high modulation and the quantization areunexpected results.To measure the thermoelectric effect, part of the loop was heated. Quasiparticles wereinjected through the Josephson junctions into the loop. Anon-trivial effectwas observedin the readout. With increasing current, the resistance decreased. In the loop interactionexperiments, a part of the loop not connected to the readout was heated. The resultsfrom the loop interaction experiments are inconclusive.We recommend that more samples are fabricated in order to repeat the result. Theobserved results should be explained theoretically as soon as possible. In futureexperiments, the induced temperature gradients must be measured.