15 October 2013
Dr John Wilson, retired George Wills Senior Research Fellow in Physics, died on 7 October after a short bout of intense illness, following prostate cancer with which he battled from 2001. Professors Nigel Hussey and Stephen Hayden offer this appreciation.
John was the only person to follow this mixed course and the particular combination of subjects was to provide an ideal base for him to develop his subsequent academic career. John’s field was Solid State Physics, informed by a strong element of inorganic/solid state chemistry.
Initially John followed Pat, his wife-to-be, to London University where he acquired a PGCE from the Institute of Education, before taking up a teaching appointment at Kings College School, Wimbledon. In 1964 John returned to the Cavendish Laboratories in Cambridge to start a PhD within the Physics and Chemistry of Solids units under a redoubtable trio of Australians, namely Professors Bowden, Tabor and his immediate supervisor, Dr A. D. Yoffe.
During this early part of his career, John made two ground-breaking discoveries in the study of phase transitions in AX2 binary systems: charge density waves in layered dichalcogenides and the Mott (metal-insulator) transition in nickel pyrites. In the late 1960s, and still in Cambridge, John noted anomalies in his diffraction, electrical transport and optical data on TaS2.
Later, in 1972, when he took up a permanent research post at Bell Telephone Laboratories in New Jersey, John showed that his observations were indeed the first experimental manifestations of charge density waves. His two review articles on this topic, published in the journal Advances in Physics, have been cited over 1,000 times and, for many, John is regarded as the father of the charge density wave phenomenon, a major sub-field of condensed matter physics and one that continues to generate worldwide interest.
A clear manifestation of the Mott transition was first discovered in 1970 in Cr-doped V2O3 by McWhan and co-workers at Bell. Two years later, John discovered the Mott transition in NiS2, an insulator that can be brought to electron delocalization (forming a metal) either by increasing pressure or by substitution of S, without any accompanying symmetry change.
NiS2 is now recognised as an ideal (text-book) system for revealing phenomena associated with the Mott transition and John’s legacy features heavily in Mott’s famous book Metal-Insulator Transitions, 2nd edition (1990).
John returned to the UK in 1979, when he was awarded a Royal Society Senior Research Fellowship at Bristol. In the years that followed, John produced an influential body of work in the area of charge density waves, including other notable discoveries such as discommensurations and the excitonic insulating state.
In the last two decades, John’s sphere of interest migrated towards understanding high temperature superconductivity. This is a controversial field; the jury is still out regarding what the underlying physics is that gives rise to the rich phenomena that are observed. John was a vociferous advocate of the, so-called, negative-U scenario.
John’s unrivalled grounding in both physics and chemistry gave him a unique perspective on condensed matter research. He was respected by his colleagues, not only for his exceptionally deep understanding of the phenomenon of charge density wave formation, but also for his encyclopaedic knowledge of materials and their physical/chemical properties.
His insistence that the physics of an individual compound could be of such complexity that understanding its behaviour might require knowledge of all facets of the material, not just a selected few, was often lost on those physicists who sought a more generic explanation. Nevertheless, John persevered and over time, proved to be a great source of information and inspiration to his more junior colleagues.
His singular devotion to his negative-U picture of high temperature superconductivity may not have won him many direct followers, but his energy in pursuing the theme certainly earned him admirers and, in time, his contributions to this iconic field might well add to his already substantial legacy.
In 1998, John received a ScD Cantab for his long-term contributions to highly correlated materials research. He was a Fellow of the Institute of Physics and of the American Institute of Physics.
After his retirement in 2003, John continued to work in the Physics Department as University Senior Research Fellow. Colleagues will recall with fondness John’s attempts to explain to non-experts, intent on eating lunch in the Hawthorns, the subtleties of a particular high temperature superconductor, and his battles with editors.
John leaves his wife Patricia Ann, his son Daniel, daughter Rebecca and many friends. Patricia Ann and John celebrated their 50th Wedding Anniversary in August 2013.
Dr John Wilson