Remembering William “Bill” Zimmermann Jr.

1930-2026

Professor Emeritus William “Bill” Zimmermann Jr. passed away in Minneapolis on July 12, 2026, at the age of 95.  Bill first joined the School as an instructor in 1959 and was on the faculty from 1961 until his retirement in 2000.  He worked with students in our advanced laboratory until 2020.   Bill was an expert on superfluidity, which formed the basis of his experimental research program.  

Bill was born in Philadelphia and raised in Wyncote, Pennsylvania.  He graduated from Germantown Friends School and received a BA in Physics from Amherst College in 1952.  While at Amherst, he worked with Professor William Fairbank, who was one of the pioneers in low-temperature physics in the United States after World War II. Bill then went on to the California Institute of Technology, where his PhD research was on low-energy nuclear physics.  After receiving his PhD in 1958, Bill received a Fulbright Fellowship to spend a year at the University of Leiden in the Netherlands, where he worked as a researcher in the Kammerlingh Onnes Laboratorium (considered the birthplace of low-temperature physics). 

Bill took what he believed would be a temporary teaching position at the University of Minnesota in 1959.  He was appointed as an Assistant Professor in 1961 and was promoted to Associate Professor in 1965 and Professor in 1970.  Bill played a key role in the expanding condensed matter physics group, which was established during the 1960’s.

Bill had a lifelong interest in superfluidity in ⁴He.  He was an expert in acoustics and hydrodynamics and developed a series of extremely sensitive experiments designed to probe the quantization of vorticity, which is the analog to flux quantization in superconductors.  Starting in the 1960’s, Bill began exploring whether an acoustic resonator could be sensitive enough to detect the motion of a single vortex across the flowpath in narrow orifices.  The approach he developed, based on a Helmholtz oscillator, was adopted by groups at Saclay in the 1980’s and Berkeley in 1990’s.   

"Bill was the paragon of a meticulous experimentalist," said Professor Paul Crowell. "His experiments were works of craftsmanship and executed with great care.  The same could be said of his teaching.  Bill cared very deeply about all of his students, from undergraduates to his own PhD advisees. For twenty years after his retirement, he mentored student projects in the School’s advanced laboratory.  Many of these were carried out in a glass dewar set he maintained so that students were able to see the superfluid transition with their own eyes."

Bill had a great variety of interests and was respected for his thoughtful approach to physics and beyond.  He was an active folk-dancer and took lessons in ballet and modern dance, performing in the Nutcracker into his 70’s.  Bill also enjoyed playing the flute.  He enjoyed the outdoors, often with his family.  He continued to ride his bike, a 3-speed Raleigh that he maintained for over 50 years, to campus into his 80’s.  Bill never stopped learning new things, such as beekeeping, which became one of his many post-retirement hobbies.  He was always curious and asked thoughtful questions, whether in a research seminar or with a grandchild.

Bill is survived by his wife Elizabeth, three children Michael (Kelty McKinnon), Sarah (Bruce Mackenzie) and Christopher (Kerstin Mueller), three grandchildren, and his sister Margaret Fonkalsrud.  He was predeceased by his brother Robert.