Michael Tinkham, renowned Harvard University physics professor and researcher, died in Portland, Oregon, on 4 November 2010 of complications following a stroke. He was Rumford Professor of Physics and Gordon McKay Professor of Applied Physics Emeritus in the physics department and the School of Engineering and Applied Sciences at Harvard University.
Born on 23 February 1928 in Green Lake County, Wisconsin, Mike graduated from Ripon College in Wisconsin in 1951 with a bachelor’s degree in physics. He received his master’s degree in 1951 and his PhD in 1954, both from MIT. His PhD thesis, “Theory of the Fine Structure of the Molecular Oxygen Ground State with an Experimental Study of its Microwave Paramagnetic Spectrum,” was supervised by Malcom Strandberg. Mike spent a postdoctoral year, 1954–55, at the Clarendon Laboratory at Oxford University, where he worked on understanding the magnetic properties of transition-metal ions in a diamagnetic lattice. He was a postdoctoral scholar in the physics department at the University of California, Berkeley, beginning in 1955, and he joined the faculty there in 1957. In 1966 he moved to the physics department at Harvard, where he spent the remainder of his career.
At Berkeley, Mike’s research was predominantly in superconductivity and magnetism. He was instrumental in elucidating the energy gap, a central component of the theory of superconductivity. In 1956, before John Bardeen, Leon Cooper, and Robert Schrieffer had presented their theory of superconductivity, Mike and Rolfe Glover III, also a postdoctoral scholar at Berkeley, measured the absorption of far-IR light passing through thin films of superconductors. They found that the light was transmitted much more readily than through a normal metal film. In the understanding at the time, it was a contradiction: Since superconductors conduct infinitely better than normal conductors, one would naively expect them to reflect light much more strongly. They contacted Bardeen, who said that the results were “not entirely unexpected.” As they increased the frequency, however, Mike and Glover found a sudden onset of absorption—at a frequency corresponding to twice the energy gap. Those experimental results, particularly the measurements of the temperature dependence of the energy gap, were a key confirmation of the theory.
Superconductivity remained Mike’s main research focus for the rest of his career. In the early 1970s, with Malcolm Beasley, Jerry Gollub, and Ron Newbower, he made important contributions to understanding the effect of thermal fluctuations on broadening the transition between the superconducting and normal states. In 1972, while on sabbatical at the University of Cambridge in the UK, he and one of us (Clarke) worked together to develop the theory of charge imbalance—the imbalance between so-called hole-like and electron-like quasiparticles above and below the Fermi surface—that results in a voltage developed at the contact between a normal metal and a superconductor. That work is an excellent example of the remarkable theoretical depth that characterized Mike’s research. With members of his group he applied those ideas to phase-slip centers, current flow across the superconductor–normal interface, and the subharmonic energy-gap structure in superconducting metallic weak links. Subsequently, Mike and his group studied submicron tunnel junctions capacitively coupled to minute islands, the Kosterlitz–Thouless transition in arrays of Josephson junctions, and tiny metallic whiskers grown on carbon nanotubes.
Mike was a gifted writer. His first book, Group Theory and Quantum Mechanics (McGraw-Hill, 1964), inspired many young students. His deep understanding of superconductivity led him to write his second book, Introduction to Superconductivity (McGraw-Hill, 1975), which clearly elucidated the subtle mysteries of the subject and has become a classic in the field.
Graduate students were attracted to Mike for his ability to make complex ideas seem simple and to offer thesis problems on the leading edge of the field. Although he stimulated his students in new directions, he gave them full freedom to follow their own ideas and develop as creative scientists. He hungered for data from his labs and had an uncanny talent for transforming scraps of experimental data into an ever-deeper understanding of superconductivity.
Mike loved good food, good wine, and, above all, desserts. His many students and postdocs were devoted to him and held an annual “Tinkham Dinner” at the March meetings of the American Physical Society. He was a modest man with a keen wit and sense of humor, and he could give and take in jesting and repartee. He once walked into his lab where some of his students were having lunch and was upset to find that none of the homemade electronics were labeled. He demanded that everything in the lab be labeled for the next generation. The next day he found all the equipment duly labeled, and his students, including the other of us (Silvera), sitting with bowed heads. When we were asked to look up, Mike saw five foreheads labeled “Graduate Student.”