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After completing my D.Phil. in theoretical physics at Oxford under the supervision of the late Dirk ter Haar,and spending three years in postdoctoral positions in Illinois,Kyoto and elsewhere,in early 1967 I had
to make up my mind as to where I wanted to spend the next few years of my
academic career.One place which had made me an offer was the
University of Sussex,which had been established a few years earlier and
had already acquired a reputation for innovation in its research and
teaching structure;this alone made it attractive to me.An additional
attraction was that the chairs in experimental low-temperature
physics and theoretical nuclear physics were held by two people,Douglas
Brewer and Roger Blin-Stoyle respectively,whom I already knew and
respected from my Oxford days.So it was not difficult to decide to accept
the offer from Sussex,and I started there as a lecturer in theoretical
physics in the autumn of 1967.
The next few years were great fun.Like my colleagues,I had what viewed
from the perspective of a major US research university seems a horrendous
undergraduate teaching load,but nevertheless found adequate time to
continue the research which I had been doing in my postdoctoral period in
low-temperature physics,interacting strongly with the Sussex experimental
group in that area and making one or two small discoveries which I found quite pleasing,in particular (with Michael Rice,then at Imperial
College) on the anomalous spin diffusion behavior of liquid 3-He.However,I
also found time to appreciate and gain from the unique interdisciplinary
ethos of Sussex at that time.One interesting aspect of the latter was
that quite a few people who were full-time members of the Physics department
were nevertheless able to spend a large fraction of their time in other
fields (and in a few cases eventually migrated full-or part-time to the
relevant sister department):Maurice Wilford devoted himself to physics
education,Roy Turner and,eventually,Norman Dombey spent much of their time
on science policy,and Brian Easlea ended up in history and social studies
of science.My thinking about the nature of physics was particularly
influenced by conversations with Brian and with Aaron Sloman,who had
started his academic career in mathematics and physics but switched his
interests to artificial intelligence.This kind of intellectual
cross-fertilization was very characteristic of Sussex at that time,and
I am sure that I was by no means the only person who benefited from it.It
was also during this period,and through Sussex,that I met my future
wife,Haruko Kinase,who entered the university in the autumn of 1970 to
read international relations and whom I first met in the University
refectory.
By the early summer of 1972 I had become somewhat bored with the rather
traditional kind of low-temperature physics which I was doing;at the same
time,thanks in large part to a mini-series of lectures by Brian Easlea,I
had become convinced that the problems in the foundations of quantum
mechanics,which I had tended to dismiss as the product of bad philosophy,
were in fact serious enough to be worth spending real research time on.I
had therefore pretty much made up my mind to work full time on the
foundations of physics (a decision which in the event I was able to
implement only some years later).In retrospect it is remarkable that this
kind of drastic switch of one's research area,which for an assistant
professor in a major US research university (and perhaps even for someone
at the corresponding level in the UK to-day) would seem like career
suicide,seemed not just possible but quite natural for a (tenure-protected!)
lecturer at Sussex in those days.
However,it was not to be.Just as I was about to junk my collection of
low-temperature reprints,my Cornell experimental colleague Bob Richardson
passed through Brighton on a flying visit and told me of the extraordinary
results that he and his colleagues had found in their ultra-low-temperature
nuclear magnetic resonance (NMR) experiments on liquid 3-He.These results
were so unexpected and intriguing that my first reaction was that maybe
they were the first evidence that under the very extreme conditions
of the experiment quantum mechanics was actually breaking down.So I decided
that before investing years of my research time in the conceptual problems
of quantum mechanics,it might be as well to make sure that the latter was
still working!
I have recounted the history of my work on what we now recognize as the
superfluid phases of liquid 3-He in detail elsewhere [1,2],so will be very
brief:Over the Sussex summer vacation I was able to show tthat the Cornell
results could indeed be understood within the framework of standard quantum
mechanics,provided that the state of the system possessed a property
which I christened "spontaneously broken spin-orbit symmetry":crudely
speaking,the nuclear spins of a pair of 3-He atoms must be uniquely
correlated with their relative positional configuration.This work was
presented by my colleague Mike Richards at the international
low-temperature physics conference in August,and drew some attention,but
there were various competing theories of what was going on in the Cornell
experiments and it was not universally accepted.For the next few months I
was mainly occupied with my teaching duties and did not have much time to
think further about the problem,but in April 1973,the Sussex Easter
vacation,I was able to visit Cornell for the whole month at the
invitation of Bob Richardson,and managed in this period to produce a
more or less satisfactory "microscopic" theory of the NMR phenomena,which
not only explained the existing data but made nontrivial predictions for
different types of experiment which were subsequently carried out.This
theoretical work is by now more or less textbook material,and was the
basis for the award to me,together with Aleksei Abrikosov and the late
Vitaly Ginzburg,of the 2003 Nobel prize in physics.
When I look back on this exciting period of my research career,then
apart from appreciating the very substantial help I got in this work
from individual colleagues such as Michael Moore and Mike Richards,I am
very grateful that I was working in the relaxed and permissive environment
that prevailed at Sussex in the early 70's.One point of particular
interest in this history is that in trying to understand the Cornell NMR
data I deliberately "rushed in where angels feared to tread",since while
I knew that there was a very well-developed existing theory of NMR,with
large books devoted exclusively to it,I had not read those books and
did not attempt to;had I done so,they would almost certainly have sent me
off in the wrong direction,since it turns out that in this context
superfluid 3-He is pretty much sui generis.I am fairly sure that had I for
example been an assistant professor at a major US research university
to-day,with my eyes fixed on the tenure process a couple of years down the
road,I would not have had the confidence to plunge into the problem as the
novice I was.This relaxed Sussex ethos persisted for the whole of my fifteen-year stay there;I would hope that some of its spirit remains even under the altered condtions of to-day.
[1]A.J.Leggett,Nobel Lectures in Physics 2003,Nobel Foundation,Stockholm
2004.
[2]D.M.Lee and A.J.Leggett,J.Low Temperature Physics,in press.
Tony Leggett,
Dept. of Physics,University of Illinois at Urbana-Champaign
Tel:(217)-333-2077
Fax: " " 9819