Superconductivity: the path of least resistance to the future

ABSTRACTThe accidental discovery of mercury's zero resistance at temperatures lower than 4.2 K which took place in 1911 by the Dutch physicist Heike Kamerlingh Onnes in his laboratory at the University of Leiden, appeared to be one of the greatest breakthroughs of physics of all time. It has led to the creation of an entirely new field within physics called superconductivity; this attracted many of the finest minds in physics whose work in this area produced no less than six Nobel Prizes to date. Zero resistance, together with the expulsion of magnetic fields which was discovered many years later, are the two unique and intriguing properties of superconductors which puzzled scientists' brains for a proper theoretical explanation of the observed phenomena. However in 1935, the phenomenological theory proposed by Fritz and Heinz London (known as the London theory) was the first success in the field, which was followed in the 1950s by another phenomenological theory put forward by Vitaly Ginzburg and Lev Landau. Despite this, a satisfactory microscopic theory for superconductivity had to wait until 1957 when John Bardeen, Leon Cooper and John Robert Schrieffer proposed their theory, which was nicknamed the BCS theory in their honour. The more recent discovery of the cuprate high temperature superconductors (HTS) in 1986 gave a new momentum to the field and intensified the search for room temperature superconductors which continues to this day. While this quest is under way, and new theories of superconductivity are being developed, physicists, material scientists and engineers are using superconductors to establish new technologies and build machines, devices and tools with unprecedented properties. Today superconductors are widely used in healthcare, particle accelerators, ultrasensitive instrumentation and microwave engineering and they are being developed for use in many other areas as well. In this review, we will trace the history of superconductors and provide a brief overview into some of the recent applications of superconductivity.KEYWORDS: Zero electrical resistanceMeissner effectflux quantisationLondon theoryGinzburg–Landau theoryBCS theoryjosephson effecthigh-temperature superconductivitysuperconductive electronicsSQUIDsuperconducting qubit AcknowledgmentsThe authors are grateful to Prof. A. Stefanovska for the invitation to write this review and her encouragements during writing. Proof-reading of the manuscript by B. Mercer is gratefully acknowledged.Disclosure statementNo potential conflict of interest was reported by the authors.Additional informationFundingYAP acknowledges partial support from the QSHS project ST/T006102/1 funded by STFC.Notes on contributorsWilliam J. MercerWilliam John Mercer was born in Preston, Lancashire; he attended Broughton High School and Runshaw College before going to Manchester University to study electrical and electronic engineering before changing to Lancaster University to study Natural Sciences. He was an exceptional student throughout, gaining 3 A*s at A Level and achieving high grades in all of his university exams. He was popular and well liked with many friends, and interests, including football, scouting and student politics. He had just finished his final exams in June 2021 at Lancaster University when an unsuspected COVID-19 infection (he was awaiting his vaccination) caused him to faint in his student house, in the process sustaining unsurvivable brain injuries; he died in hospital two days later. He received a posthumous first class honours degree from Lancaster. William's death was a tragic loss not only to his family and friends, but also to the scientific community; this article was drawn from his final year dissertation and serves as a fitting tribute to him.Yuri A. PashkinYuri A. Pashkin received his Master's degree from Moscow State University, followed by his PhD degree from Moscow's Lebedev Physical Institute where he began his research career as a Junior Research Fellow. He was then promoted to Research Fellow and later to Senior Research Fellow. During this time, he also worked as a Visiting Researcher at Chalmers University of Technology (Sweden), Physikalisch-Technische Bundesanstalt (Germany) and the University of Jyvaskyla (Finland). In 1997, he moved to Japan to become a Researcher and subsequently Principal Researcher at the laboratory of NEC Corporation in Tsukuba where he conducted ground-breaking experiments on superconducting quantum devices and co-authored several influential and highly cited papers in the field. While at NEC, he was a Visiting Professor at Aalto University and VTT (Finland). Yuri joined Lancaster University in 2011 to take up the position of Chair of Experimental Condensed Matter Physics in the Department of Physics. In 2012, he relocated to the UK to lead the launch of Lancaster University's Quantum Technology Centre which he then directed for five years. In the same year he was awarded the Royal Society Wolfson Research Merit Award in recognition of his distinguished contributions to Physics. In 2014, he was made a Fellow of the Institute of Physics because of his substantial contribution to the field of superconducting quantum devices. His research is focused on nanoscale electronic and elecromechanical devices with particular interests in quantum computing, quantum metrology and quantum sensing.