The death on June 12, 2009 of Robert Powell Guertin, long‑time Professor of Physics and former Dean at Tufts University and a highly respected figure in experimental condensed matter physics, spread shock and sorrow among his many friends and colleagues.
Born in Trenton, New Jersey, and raised in Winnetka, Illinois, Bob was educated at Trinity College in Hartford, Wesleyan University and the University of Rochester before joining the Tufts faculty in 1968. He spent his entire academic career at Tufts, but his research took him to the Francis Bitter National Magnet Laboratory at MIT and its successor, the National High Magnetic Field Laboratory at Florida State University, as well as Los Alamos National Laboratory and the University of California, San Diego. His ability to identify scientific questions that were both important and tractable, his leadership and interpersonal skills, and his remarkable energy led to long and productive collaborations with numerous distinguished scientists, including Simon Foner, Jack Crow, Brian Maple and Zachary Fisk.
As a researcher, Bob was drawn to extremes. He specialized in measuring the properties of exotic materials in high magnetic fields, at high pressures, and at low temperatures — often all three at once. He and Foner adapted Foner's vibrating sample magnetometer to enable sensitive measurements of magnetic moments under the simultaneous influence of high magnetic fields and high hydrostatic pressures.
His experiments focused on highly correlated materials and frequently provided stringent tests of prevailing theories. His research on high‑temperature superconductors, for example, tested whether magnetic impurities would reduce Tc according to the Abrikosov‑Gorkov theory, or whether nonmagnetic impurities would produce pair breaking as expected for non‑s‑wave pairing mechanisms. He found that increasing Pr concentration in YBa2Cu3O7 decreased Tc according to the A‑G theory, indicating spin‑singlet Cooper pairing. However, the Néel temperature decreased with increasing Y content, indicating the coexistence of antiferromagnetism and superconductivity. These early results helped identify the unconventional nature of the superconducting order parameter in the high Tc materials.
His studies of ternary iron phosphide compounds identified multiple interesting phases, including superconductivity in LaFe4P12, ferromagnetism in UFe4P12, and antiferromagnetism in PrFe4P12 and NdFe4P12. His studies of semiconducting behavior in UFe4P12 helped lay the foundation for the renormalized hybridization gap picture of Kondo insulators. In recent years, Bob applied his extensive experience to bring conceptual coherence to the rich phase diagrams of the 4d‑ruthenate transition metal oxides, showing that the metal‑oxide‑metal bond angle is a key parameter in the formation of the enhanced Fermi‑liquid state.
But Bob's love of extremes did not extend beyond the laboratory. As a teacher, mentor, colleague and friend, he was a model of equanimity, modesty, good judgment, generosity and good humor. While he took his work very seriously, especially his research and work with students and younger colleagues, he could also look at the world — physics, teaching, Tufts, politics, the Red Sox — with "a mischievous twinkle in his eye," as a colleague put it. After dealing with a complaining student, an unreasonable review of a paper, an aggravating faculty meeting, or a challenging physics problem, the best place to go was the couch in Bob's office — though there was sometimes a wait. Whatever the annoyance or complexity, Bob's combination of careful thought and sense of humor always put it in perspective. No wonder, as Tufts President Larry Bacow put it, "there were few people who ever worked at Tufts who were as beloved and respected as he was."
He served eleven years as Dean of the Tufts Graduate School of Arts and Sciences, enhancing its size and stature through his good judgment, leadership and organizational abilities, and commitment to outstanding education and first‑rate research. He was a passionate advocate for students and the driving force behind the 89,000‑square‑foot Tufts University Science and Technology Center, a multi‑discipline research center. He involved himself in every detail from securing funding through its design and construction. The flourishing research environment at this well‑engineered and versatile structure is a testament to his vision and energy. Somehow amidst his active research and administrative responsibilities he found time to serve on numerous NSF panels, external review committees, conference organizing committees, and as Chair of the Board of Governors of the University Press New England.
In his last few months, as his health began to fail and his growing pain was apparent, he devoted much of his remaining strength to teaching his class in Classical Mechanics — he was determined not to let his students down. Equally important to him was not to be a burden on the department or his colleagues. To the very end he was always thinking of others, and devoted to Physics, to Tufts and to all the people who had come to love and depend upon him for selfless service and gentle wisdom.
