PHOTO: ADAM FENSTER/UNIVERSITY OF ROCHESTER520 29 OCTOBER 2021 • VOL 374 ISSUE 6567 science.org SCIENCEA
result last year hailed as a break-
through in physics also generated
skepticism that has now escalated
into angry recriminations. Research-
ers said they had made the first
superconductor that works at room
temperature, a long-sought goal. But Jorge
Hirsch, a physicist at the University of Cali-
fornia (UC), San Diego, attacked some of the
evidence, particularly a set of magnetic mea-
surements. He says his requests to see the
underlying data have been rebuffed by the
authors for nearly a year. And, last month in
a peer-reviewed paper, he charged that the
results are “probably fraudulent.”
Ranga Dias, an applied physi-
cist at the University of Rochester,
who with his colleagues made the
room-temperature superconductiv-
ity claim, rejects Hirsch’s allegations.
He asserts that Hirsch isn’t an expert
in high-pressure physics and that he
has a history of claiming that the
Nobel Prize–winning “BCS theory”
underlying superconductivity is in-
correct. Dias says Hirsch relentlessly
badgers superconductivity research-
ers. “Hirsch is a troll,” Dias says. “We
are not going to feed this troll” by
providing the data.
Superconductivity is normally
seen only at temperatures well below
200 K, or –73°C. But several research
groups working with hydrogen-rich
compounds called hydrides have reported
that they became superconductors between
200 K and 250 K when squeezed to intense
pressures. Dias and his team went further.
They reported that by adding a bit of carbon
to precursors of H 3 S, a known hydride super-
conductor, they were able to create a carbon
sulfur hydride (CSH) material that pushed
the superconducting temperature up to
287 K (14°C), the temperature of a cool room.
The result, published in the 15 October 2020
issue of Nature, drew worldwide acclaim
(Science, 16 October 2020, p. 273).
Some scientists attempted to replicate or
extend the finding, without much success.
And Hirsch and others raised concerns
(Science, 27 August, p. 954). Like other
superconductors, CSH showed a charac-
teristic plunge in electrical resistance as
it dropped below the “critical tempera-
ture” (Tc) and became a superconductor.
To confirm that a material superconducts,
however, physicists also look for a second
telltale indicator, known as the Meissner ef-
fect, in which the material expels magnetic
fields below Tc.
Measuring the Meissner effect hasn’t been
possible in hydrides because they are formed
in minute amounts inside a high-pressure
device called a diamond anvil cell, which
normally is made from magnetic materials.
So, hydride researchers have instead evalu-
ated a property known as AC susceptibility,
a measure of how much a material becomes
magnetized in an applied magnetic field. In
Dias’s Nature paper, CSH’s AC susceptibilitydropped sharply at Tc, consistent with the in-
terpretation that the material was expelling
magnetic fields.
But the data also show that as the mate-
rial cools below Tc, the AC susceptibility rises
again. That’s a behavior not usually seen in
superconductors, Hirsch argues, though oth-
ers say the behavior has been seen in other
superconductors under high pressure.
Hirsch also contends some of the AC sus-
ceptibility data for CSH look suspiciously
similar to other data that are now in ques-
tion, from a 2009 Physical Review Letters pa-
per on superconductivity in europium under
high pressure. One of that study’s authors is
James Hamlin, a physicist now at the Uni-
versity of Florida, who participated in the
europium study as a graduate student. He
recently determined that “there are altera-
tions to the data.” The study’s senior author,James Schilling, an emeritus physicist at
Washington University in St. Louis, says he
shares that concern. Now, some of the co-
authors are redoing the measurements, and
if they don’t hold up, the team will retract
the paper, Hamlin says.
The first author of the europium paper,
Mathew Debessai, now with Intel Corpora-
tion, was responsible for the AC susceptibil-
ity measurements, and also carried out those
measurements for Dias’s CSH work. And
a data trace from the CSH paper looks “re-
markably similar” to one from the europium
paper, Hirsch contends. Schilling agrees parts
of the traces do look similar, but he can’t say
why. Debessai declined to respond to ques-
tions about the data but via email
wrote that he will post a formal re-
sponse on the arXiv preprint server.
In October and November 2020,
Hirsch emailed Dias requests for raw
data. Dias replied that he would not
provide the data for reasons includ-
ing that his team was working to pat-
ent the work, and his lawyer advised
against releasing the data. By then,
Hirsch had raised concerns about
the CSH data in a preprint, which
was published in Nature in August.
In his email to Hirsch, Dias wrote,
“Given that you have an active com-
ment on our work, we consider such
a request would not be reasonable.”
Frustrated, Hirsch requested the
data from Nature and the National
Science Foundation (NSF), which
funded the work. On 30 August, Nature ap-
pended a note to Dias’s paper saying: “The
editors of Nature have been alerted to un-
declared access restrictions relating to the
data behind this paper. We are working
with the authors to correct the data avail-
ability statement.” NSF and the University
of Rochester both tell Science they cannot
comment on possible investigative matters.
Then, last month in Physica C: Super-
conductivity and its Applications, Hirsch
wrote that Dias’s anomalous AC susceptibil-
ity result, combined with seeming irregular-
ities in the europium data, and his struggles
to get the data on CSH, fed his doubts. “I
suggest that one possible explanation is
that [the CSH finding] is the result of data
manipulation and alteration such as was
described ... for [europium],” Hirsch wrote.
Alexander Goncharov, a physicist at theHIGH-PRESSURE PHYSICS
Superconductor finding draws pointed critique
Study slammed by critic, who has demanded raw data withheld by authors
By Robert F. Service
Ranga Dias’s room-temperature superconductor paper is under fire.NEWS | IN DEPTH