Closing remarks

Closing remarks Chairman, Ladies and Gentlemen, it is my privilege to make the closing remarks at this conference. The two most important tasks before me are to thank all those who have made the conference possible and to announce the location of the next conference in this series. However, custom demands that before I do this I keep you a little longer and say something about the state of health of our subject and about my impressions of this conference. The scope and success of this conference provide ample evidence for the good health of our subject. The meeting has been attended by some 1200 scientists from all over the world, who have presented over 1000 papers. Those 1200 scientists include people who, like me, have enjoyed working in our subject for over 30 years, but also many of the young people who are still being drawn into the subject and find it just as fascinating and challenging as it was for those of my generation all those years ago. Sadly, no one person can attend all the sessions of a conference like this, and my impressions are based on only the small number of sessions that I have been able to attend. Our last conference, in Kyoto in 1987, took place shortly after the discovery of the high-temperature superconductors. Almost half the papers at our present conference are devoted to this subject. But the subject has now acquired a certain maturity, and photographers and others from the press no longer invade our sessions as they did in Kyoto. As we have seen here, this maturity has been accompanied by a pleasing degree of agreement on the experimental facts, by a multitude of theoretical ideas, and by a complete lack of agreement on a theory relevant to the actual phenomena. That is a wonderfully healthy situation, quite similar in some ways to the one existing in conventional superconductivity when I was a graduate student, except that even the normal state in the HTSs is not yet understood. Much the same is true for the heavy-fermion metals, where clear evidence for exotic forms of superconductivity have now been found. Both systems reveal subtle combinations of many-body effects, such as magnetic fluctuations and superconductivity, about which we still have an enormous amount to learn. I find it marvellously invigorating that we keep on finding quantum mechanical many-body systems exhibiting new and fascinating forms of behaviour, a point to which I shall return later. The high-temperature superconductors and the heavy-fermion metals have involved new kinds of material studied experimentally in largely traditional ways. But’ new experimental techniques have also brought us new phenomena and allowed us to look in more detail at old phenomena. Microfabrication techniques have brought us new insights: into the behaviour of normal-metal mesoscopic systems; into quantum ballistic transport; into macroscopic quantum tunnelling: and into effects relating to the Coulomb blockade in which single electron tunnelling events are observable. The scanning tunnelling microscope, and other imaging techniques, are giving us pictures of low-temperature structures of a type that would have been difficult even to imagine a few years ago. Modern techniques, such as MBE, for the precise fabrication of layered structures are continuing to lead to new studies of low-dimensional systems, including, for example, the successful search for magnetically induced crystallization in degenerate two-dimensional electron systems and some beautiful and important work on superconducting layered structures. Ultra-low temperature techniques continue to develop, and I was particularly impressed by the studies of nuclear ordering in copper and silver by neutron scattering at nanokelvin temperatures (this is the first conference at which I have heard temperatures quoted in picokelvins!). But we must not forget that old phenomena must always be kept under review, in the way, for example, that we have seen at this conference in discussions of the low-temperature behaviour of glasses. Such reviews often lead to

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Closingremrrrks

new and important insight. And finally we must not forget the steady progress that is still being made in the traditional areas of our subject, such as the study of superfluidity in the two isotopes of helium. The unity of low-temperature physics still impresses me. The cross-fertilization between its different parts continues to be very important and is greatly facilitated by our conferences. The connections between the superconductivity in the heavy-fermion metals and superfluidity in ‘He is an obvious example. Nicholas Kurti reminded us in his address at the opening ceremony of the gloomy view of low-temperature physics expressed by a few people at the seventh meeting in this series in Toronto in 1960: that low-temperature physics did not exist, or, worse still, that if it did exist it was doomed to an early death. Every low-temperature conference since then has shown how wrong this view was, and this conference is no exception. What we continually see is that the quantum mechanical many-body systems and other forms of condensed matter with which we are concerned can exhibit a number and variety of types of behaviour that seems without limit. I see no end to it. I venture to suggest therefore that, far from being close to its demise, low-temperature physics will have everlasting life. I come now to the most important parts of my task. First, I must thank very warmly all those who have made this conference possible. The organization of the conference has relied to some extent on a national effort, but inevitably the major load of work and responsibility has fallen on a small group of people. On this occasion I have seen closely how large that load is and how grateful we ought to be that there are those in our community who are willing to accept it. Professor Brewer has already given you the names of those involved, and I add my thanks to his. I would like also to thank all our participants, expecially those presenting papers, which have been of an exceptionally high standard, both in their scientific interest and in the way they have been presented. But above all, and on behalf of us all, I must thank very sincerely our Chairman, Douglas Brewer, who has carried the ultimate responsibility and has had to deal with all the difficult problems and decisions that conferences of this kind always generate. To you, Douglas, we are all very grateful for making this conference such a success. Finally, ladies and gentlemen, I must tell you about the next conference in this series. The IUPAP Commission on Low Temperature Physics met at the end of last week and received two offers to host the next conference. Both offers were very well prepared and attractive, and I would like to thank the authors of both for all the work they put in. However, the commission had to make a decision, and I can tell you that the proposal by Professor R.J. Donnelly that LT-20 should be held in Eugene, Oregon, in August 1993 has been accepted. We are all very grateful to Russell Donnelly for his willingness to carry the heavy load of work and responsibility that will be involved. With this announcement I close this conference. I say farewell to you all and look forward to seeing you again when we reconvene in Oregon in 1993. Professor

W.F. Vinen