The Nobel Prize in Physics 1987
J. Georg Bednorz, K. Alex Müller
Presentation Speech by Professor Gösta
Ekspong of the Royal Academy of Sciences
Translation from the Swedish text
Your Majesties, Your Royal Highnesses,
Ladies and Gentlemen.
The Nobel Prize for Physics has been awarded to Dr. Georg Bednorz and Professor Dr. Alex Müller by the Royal Swedish Academy of Sciences "for their important breakthrough in the discovery of superconductivity in ceramic materials". This discovery is quite recent - less than two years old - but it has already stimulated research and development throughout the world to an unprecedented extent. The discovery made by this year's laureates concerns the transport of electricity without any resistance whatsoever and also the expulsion of magnetic flux from superconductors.
Common experience tells us that bodies in motion meet resistance in the form of friction. Sometimes this is useful, occasionally unwanted. One could save energy, that is to say fuel, by switching off the engine of a car when it had attained the desired speed, were it not for the breaking effect of friction. An electric current amounts to a traffic of a large number of electrons in a conductor. The electrons are compelled to elbow and jostle among the atoms which usually do not make room without resistance. As a consequence some energy is converted into heat. Sometimes the heat is desirable as in a hot plate or a toaster, occasionally it is undesirable as when electric power is produced and distributed and when it is used in electromagnets, in computers and in many other devices.
The Dutch scientist Heike Kamerlingh-Onnes was awarded the Nobel Prize for Physics in 1913. Two years earlier he had discovered a new remarkable phenomenon, namely that the electric resistance of solid mercury could completely disappear. Superconductivity, as the phenomenon is called, has been shown to occur in some other metals and alloys.
Why hasn't such an energy saving property already been extensively applied? The answer is, that this phenomenon appears only at very low temperatures; in the case of mercury at -269 degrees Celsius, which means 4 degrees above the absolute zero. Superconductivity at somewhat higher temperatures has been found in certain alloys. However, in the 1970's progress seemed to halt at about 23 degrees above the absolute zero. It is not possible to reach this kind of temperatures without effort and expense. The dream of achieving the transport of electricity without energy losses has been realized only in special cases.
Another remarkable phenomenon appears when a material during cooling crosses the temperature boundary for superconductivity. The field of a nearby magnet is expelled from the superconductor with such force that the magnet can become levitated and remain floating in the air. However, the dream of frictionless trains based on levitated magnets has not been realisable on a large scale because of the difficulties with the necessarily low temperatures.
Dr. Bednorz and Professor Müller started some years ago a search for superconductivity in materials other than the usual alloys. Their new approach met with success early last year, when they found a sudden drop towards zero resistance in a ceramic material consisting of lanthanum-barium-copper oxide. Sensationally, the boundary temperature was 50 % higher than ever before, as measured from absolute zero. The expulsion of magnetic flux, which is a sure mark of superconductivity, was shown to occur in a following publication.
When other experts had overcome their scientifically trained sceptiscism and had carried out their own control experiments, a large number of scientists decided to enter the new line of research. New ceramic materials were synthesized with superconductivity at temperatures such that the cooling suddenly became a simple operation. New results from all over the world flooded the international scientific journals, which found difficulties in coping with the situation. Research councils, industries and politicians are busily considering means to best promote the not so easy development work in order to benefit from the promising possibilities now in sight.
Scientists strive to describe in detail how the absence of resistance to the traffic of electrons is possible and to find the traffic rules, i. e. the laws of nature, which apply. The trio of John Bardeen, Leon Cooper and Robert Schrieffer found the solution 30 years ago in the case of the older types of superconductors and were awarded the Nobel Prize for Physics in 1972. Superconductivity in the new materials has reopened and revitalized the scientific debate in this field.
Herr Dr Bednorz und Herr Professor
In Ihren bahnbrechenden Arbeiten haben Sic einen neuen, sehr erfolgreichen Weg fir die Erforschung und die Entwicklung der Supraleitung angegeben. Sehr viele Wissenschaftler hohen Ranges sind zurzeit auf dem Gebiet tätig, das Sie eröffnet haben.
Mir ist die Aufgabe zugefallen, Ihnen die herzlichsten Glückwünsche der Küniglich Schwedischen Akademie der Wissenschaften zu übermitteln. Darf ich Sie nun bitten vorzutreten um Ihren Preis aus der Hand Seiner Majestät des Königs entgegenzunehmen.
From Nobel Lectures, Physics 1981-1990, Editor-in-Charge Tore Frängsmyr, Editor Gösta Ekspång, World Scientific Publishing Co., Singapore, 1993
Copyright © The Nobel Foundation 1987