I would characterize myself primarily as a developer of the methodology of (and facilities for) muon spin rotation/relaxation/resonance (ÁSR) and as a promoter of its wider use as a general-purpose tool of material science and chemistry. Reference 1 summarizes the origins, methodology and applications of ÁSR.
Over the years I have also maintained an active interest in the more fundamental aspects of muon science as well as the practical aspects of muon beam technology, but ÁSR remains my first love. In the past two decades, I have helped to build up world-class ÁSR facilities at TRIUMF that are unique in the Western Hemisphere; I am now working to make those facilities more available to other ÁSR users, such as the 100 or more condensed matter physicists and chemists who visit TRIUMF regularly from all over the world to perform ÁSR experiments on their chosen systems - gases, liquids and solids.
The following papers exemplify my group's most rewarding contributions to the field of high temperature superconductivity (HTSC), the primary focus of my research since I was invited to join the Superconductivity program of the Canadian Institute for Advanced Research in 1988: The review article, Ref. 2 below, describes a decade-long study of the temperature- and magnetic field-dependence of the magnetic penetration depth and the coherence length in various superconductors, primarily the archetypal HTSC YBa2Cu3O6+x, using HTF-µ+SR lineshape measurements refined at TRIUMF since 1987. This method has also been used to investigate the dynamics of the vortex lattice in HTSC. A recent paper, Ref. 3, describes our recent confirmation of weak magnetism in extremely pure, superconducting YBa2Cu3O6+x crystals. This phenomenon is the primary focus of my research as of 2001.
Another major area of ÁSR research involves the behaviour of muonium (Á+e-) atoms in nonmetals. A prime example of how ÁSR experiments provide the best tests (indeed, in this case the only test) of theories of quantum propagation with dissipation is described in Ref. 4. More recently, in Ref. 5 we have found the first known example of destruction of bandlike propagation by order (in this case orientational order); normally one expects disorder to have this effect, as in "Anderson localization".
Our subsequent work on this and other cryocrystals (materials that are normally gaseous at room temperature) showed that muonium is ubiquitous in these simple insulators and that studies of the electric field dependence of the details of its formation can reveal both qualitative features of muon solid state chemistry and quantitative measurements of the mobility of charge carriers liberated in the muon's ionization track. In Ref. 6 we describe how this new technique can be used to investigate charge transport; these studies have since been extended to more conventional insulators and semiconductors.
These examples are referenced above: