Neil W. Ashcroft (1938-2021)

Neil W. Ashcroft (1938-2021).

When Neil Ashcroft died on March 15, 2021, there came across our community of high pressure science a more than usual sense of loss. For this wonderful person was so much more than just a leading scientist of the field – so many of us, young and old, understood that we had lost a motive, positive unifying force, the clearest of teachers, and a conscience of the profession. Neil Ashcroft stood consistently for the best our science could do. And the adventure of extreme pressure.

The beginnings of Ashcroft’s life are tied to New Zealand and the UK in change with World War II. Neil was born in London, November 27, 1938 (he remembered blackouts and bombing raids from wartime), then came with his family to New Zealand after the War. Neil grew up in Petone near Wellington, New Zealand, and went on to study mathematics and physics at what is now Victoria University of Wellington. He then returned to the UK, undertook PhD studies supervised by John Ziman and Volker Heine at Cambridge University, where he was an early member of Churchill College.

Neil studied the Fermi surface of metals as it relates to their electronic properties. In 1964 he went on to the University of Chicago as a Postdoctoral Research Fellow and then in 1965 to Cornell University, where he remained for the rest of his research career. A life in service – to his university, to the high pressure community, to world physics - followed. All his life, Neil worked for us. At Cornell, he became Director of the Cornell High Energy Synchrotron Source, Director of the Cornell Center for Materials Research. Nationwide, he consulted for every national laboratory of note, and was a member of the Editorial Board of The Physical Review. Following long involvement with Gordon Research Conferences he became Chair of the Board of GRC Trustees. There is no photograph of the Gordon Research Conference on Research at High Pressure that does not feature Neil.

Neil became Chairman of the Division of Condensed Matter Physics, American Physical Society. He loved to tell of his organization of the “Woodstock of Physics”, the night of March 18, 1987, where the first extensive reports on high temperature superconductivity were presented in a crammed session that ran through the night and well into the early hours of the next morning.

Woodstock of Physics: High Temperature Superconductivity (Part 1 of 8): watch on YouTube.

Among his many honors, Ashcroft was a member of the National Academy of Sciences, the American Association for the Advancement of Science, a fellow of the American Physical Society, an honorary fellow of the Royal Society of New Zealand, a foreign member of the Russian Academy of Sciences, a Guggenheim Memorial Fellow, and winner of the 2003 Bridgman Award in high pressure physics, awarded by the International Association for the Advancement of High Pressure Science and Technology (AIRAPT).

Neil is survived by his wife of 60 years, Judith, his sons Robert and Ian, and their families.

The readers of this obituary know very well Neil Ashcroft’s contributions to physics and to research on matter at high density, high pressure. There is no part of the world that entices us that Neil has not touched. But his most tangible legacy may have been “Solid State Physics,” written with his friend and colleague, David Mermin. Upon its publication in 1976 the book was immediately translated into Polish, Russian and Japanese, and later made its way into German, French and Portuguese, as well as physics classrooms around the world.

“For the generation of physicists reared during the last quarter of the 20th century, Neil Ashcroft and David Mermin’s textbook was the go-to bible of the field,” said Sol Gruner, a colleague in physics at Cornell. “The textbook was so ubiquitous that the title, “Solid State Physics,” was rarely mentioned. Rather, people said simply ‘Check it out in Ashcroft and Mermin.’”

When Physics Today published an article in 2013 that both praised the book and questioned whether it needed to be updated to keep pace with scientific advances, Ashcroft wrote in response, “…laudatory comments about our book are generous in the extreme. David and I are both grateful, and together we hope that the aging process, of ourselves and of our textbook, will not unduly accelerate.”

“Neil Ashcroft was a colleague and close friend for over 50 years. The happiest years of my professional life were the six years Neil and I spent writing our book ‘Solid State Physics,’” Mermin said. “Neil had a wonderful sense of humor. The fun we were having permeates the book. It’s still thriving 45 years after it came out, still in its original edition. Unlike almost all technical books, I believe ours entertains the reader in much the same way that Neil and I entertained each other while writing it.”

Mermin was not the only one entertained by Neil’s quiet wit. Everyone who came in contact with him remembers his charm, his storytelling. I came to know Neil well only 40 years after we had both come to Cornell. Neil’s son, Robert, puts it this way: “Following his formal retirement in 2006, Ashcroft exhibited an unexpected new burst of scientific activity. After a serendipitous meeting Ashcroft joined Roald Hoffmann’s research group. Their interdisciplinary collaboration was so productive it amounted to a research renaissance for Ashcroft.” I would put it another way: It took a brave postdoc, Wojciech Grochala, to bring us together. But then we were off and running, for fifteen years of scientific joy.

In 47 joint scientific papers over 15 years and in countless group meetings, I and my coworkers learned from Neil Ashcroft. And so did the community. Neil was wise and perceptive, fascinated by the border between Chemistry and Physics. I would say that he was respectful of the understanding that chemists had reached of a complex world; he really wanted to learn how we did it.

Over the years Ashcroft’s research interests encompassed many areas, including: density functional theory, matter at extreme densities and in reduced
dimensionality, strongly correlated many-particle systems, superlattice heterostructures, metal-insulator transitions, metallic hydrogen and its alloys, the
general theory of superconductivity, and high-temperature superconductivity.

Ashcroft not only helped shape the fundamentals of his field. He also had a knack for anticipating its future discoveries. When his research group predicted in the 1990s that compressed lithium would transition from a highly symmetric structure, its atoms closely packed, to a less symmetrical structure with some electrons off the lithium nuclei, that risky prediction was quickly confirmed. Ashcroft’s suggestion, originally made two decades ago, that high-temperature superconductivity could also be found in hydrogen-rich materials at extreme pressure, was realized in the past 5 years when several research groups reported superconductivity at very high and near-ambient temperatures for SH3, LaH10 , and a mixture of C, S and H.

Very important for a competitive research area at the frontiers of physics was Neil’s ability for peaceful resolution of potential contention – he had a special way of summarizing the good science that was the central achievement, and bringing all of us together in thankful recognition of the surprising science, the essential advances. Calm and wit were at the core of his strategy. Young people and older ones looked to Neil for understanding. He stood for that. And somehow he convinced us that physical and chemical understanding was within our reach. As it is.

We miss him.

Roald Hoffmann
Cornell University