If you have an ACS member number, please enter it here so we can link this account to your membership. (optional)

ACS values your privacy. By submitting your information, you are gaining access to C&EN and subscribing to our weekly newsletter. We use the information you provide to make your reading experience better, and we will never sell your data to third party members.


Electronic Materials

Reactions: Proving room-temperature superconductivity, and remembering Rudy Baum

May 20, 2022 | A version of this story appeared in Volume 100, Issue 18


Letters to the editor

Room-temperature superconductivity

The report of room-temperature superconductivity in hydride materials at extremely high pressures has attracted not only worldwide interest but also controversy (C&EN, Oct. 19, 2020, page 7).

We present a historical perspective: After the 1987 report of high-temperature superconductivity at 90 K in a cuprate material (subsequently identified as YBa2Cu3O7, also called ‘1-2-3’), Sir Brian Pippard took the strong line that a genuine Meissner effect—the expulsion of an applied magnetic field below Tc—must be demonstrated visually to confirm superconductivity. This required either supporting the cuprate superconductor’s weight above a strong-enough permanent magnet—that is, levitation—or “chasing” the superconductor in liquid nitrogen with a magnet. Sir John Meurig Thomas recounted to one of us (Peter P. Edwards) that Pippard originally disbelieved the report. Another of us (Adrian Porch) was present at a subsequent demonstration in the spring of 1987 at the Cavendish Laboratory, in England, when granules of a black-green mixed-phase 1-2-3 sample (containing green Y2BaCuO5) were indeed “chased” around by a magnet at the bottom of a glass vessel containing liquid nitrogen. On the basis of this visual demonstration, Pippard instantly acquiesced that superconductivity at 77 K in the sample was genuine (an example of professor Neil Ashcroft’s statement to one of us, Peter P. Edwards, on Sept. 4, 1997, that “a demonstration convinces a reasonable man.”)

Those seeking an unequivocal experimental confirmation of room-temperature superconductivity should at least be cognizant of Pippard’s challenge: either demonstrate levitation or, at the very least, the ability to chase the assumed superconducting specimens with a strong magnet. However, one readily concedes that similar demonstrations in these highly pressurized hydride systems would be incredibly challenging—perhaps even impossible. In that context, authenticated graphs of precipitous drops in both resistivity and magnetic susceptibility could be accepted as likely arising from superconductivity at room temperature.

Peter P. Edwards, Adrian Porch, and Daniel Slocombe
Oxford, England, and Cardiff, Wales

Rudy Baum

Thank you for the excellent article about Rudy M. Baum (C&EN, April 18, 2022, page 37). During a period when the American Chemical Society was among the most conservative of the national scientific societies, Baum’s editorials re important science policy issues were brilliant, fair, informative, and often counter to official ACS policy. I hope ACS will organize a science policy fellowship in his honor.

David L. Garin
Saint Louis

I’m also saddened by the reports of the death of Rudy Baum, former editor in chief of C&EN. I had a chance to meet Rudy at an ACS meeting years ago and found him very approachable and a great conversationalist. Lauren Wolf’s observation that Rudy was an introvert but also a great leader and people person resonated with this fellow introvert. Introverts aren’t necessarily wallflowers but can be people persons and yes, leaders, educators, and mentors. It’s just that we have to recharge our batteries alone or with family.

Rudy definitely did not shun controversial topics, especially climate change. His observations, editorials, and book reviews were presented in a fair and factual way. However, this opened him up to scathing (and unfair and insulting) comments or letters by readers who described him in partisan political terms. To show fairness, he published these attacks even though he was not attacking them.

I was most impressed with Rudy’s book reviews either in editorials or stand-alone book reviews. This continued a tradition begun in previous editorships but which has unfortunately since lapsed. I was just beginning my secondary career as a book reviewer (more than 200 for several venues), and most of our e-conversations, often personal rather than formal letters to the editor, revolved around the need for book reviews in the sciences and chemistry and related topics. About the same time that Rudy and C&EN were promoting book reviews, other ACS journals and venues were ceasing book review publication. I strongly recommend that C&EN promote book reviews, not only in editorials (which occasionally occurs) but also in stand-alone publications. His reviews that continued after he became “roving editor” were most welcome; many of us were sad to see them go.

I also regret the cessation of online comments in the digital version. Restoration of comments and book reviews will enhance the mission of ACS and C&EN to enhance communication. Rudy also mentored a generation of science journalists, a profession in need of excellence in practitioners and content.

Rudy, your legacy is profound in many areas. I’m honored to have known and conversed with you. You are sorely missed.

Robert E. “Bob” Buntrock
Orono, Maine



This article has been sent to the following recipient:

Chemistry matters. Join us to get the news you need.