Jess H. Brewer's Research

I would characterize myself primarily as a developer of the methodology of (and facilities for) muon spin rotation/relaxation/resonance (µSR) and as a promoter of its wider use as a general-purpose tool of material science and chemistry. The following article summarizes the origins, methodology and applications of µSR: J.H. Brewer, ``Muon Spin Rotation/Relaxation/Resonance", Encyclopedia of Applied Physics 11 (Mößbauer Effect to Nuclear Structure), 23-53 (1994). 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 µSR remains my first love. In the past decade, I have helped to build up world-class µSR facilities at TRIUMF that are by far the best in North America; I am now working to make those facilities more available to other µSR users, such as the 120 or more condensed matter physicists and chemists who visit TRIUMF regularly from all over the world to perform µSR experiments on their chosen systems - gases, liquids and solids.

The following two 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 first, J.E. Sonier, R.F. Kiefl, J.H. Brewer, D.A. Bonn, J.F. Carolan, K.H. Chow, P. Dosanjh, W.N. Hardy, Ruixing Liang, W.A. MacFarlane, P. Mendels, G.D. Morris, T.M. Riseman and J.W. Schneider, "New Muon-Spin-Rotation Measurement of the Temperature Dependence of the Magnetic Penetration Depth in YBa₂Cu₃O_6.95", Phys. Rev. Lett. 72, 744-747 (1994). describes our confirmation of the linear temperature dependence of the magnetic penetration depth in YBa₂Cu₃O_6.95, a result that is widely regarded as conclusive evidence for a "d-wave" pairing mechanism in this archetypal HTSC. The second (submitted) paper extends those investigations to the magnetic field dependence of - the theoretical impact of which may be even greater: J.E. Sonier, R.F. Kiefl, J.H. Brewer, D.A. Bonn, S.R. Dunsiger, W.N. Hardy, Ruixing Liang, W.A. MacFarlane and T.M. Riseman, "Magnetic Field Dependence of the London Penetration Depth in the Vortex State of YBa₂Cu₃O_6.95", submitted to Phys. Rev. Lett. (1996).

We are now studying the temperature- and field-dependence of the coherence length in both HTSC and conventional superconductors where it has never been measured in the mixed state at low T. New experimental techniques (high field, high time resolution, low background methods) are being developed for these challenging measurements.

Another major area of µSR research involves the behaviour of muonium (µ⁺e^-) atoms in nonmetals. A prime example of how µSR experiments provide the best tests (indeed, in this case the only test) of theories of quantum propagation with dissipation is described in V.G. Storchak, J.H. Brewer, W.N. Hardy, S.R. Kreitzman and G.D. Morris, "Two-Phonon Quantum Diffusion of Muonium in Solid Nitrogen", Phys. Rev. Lett. 72, 3056-3059 (1994).

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 the paper V. Storchak, J.H. Brewer and G.D. Morris, "Fast and Slow Electrons in Liquid Neon", Phys. Rev. Lett. 76, 2969-2972 (1996) we describe the prototype example of this new technique for investigating charge transport; we are now extending the technique to more conventional insulators and semiconductors.