In 1997, Carnegie and Russian scientists turned sulfur into a superconductor at 93 GPa. 29 years later, the discovery still helps physicists understand materials that can conduct electricity without resistance

A piece of ordinary sulfur does not look like the kind of material that could rewrite the rules of electricity. At normal pressure, sulfur is an insulator. But squeeze it hard enough—about 93 gigapascals—and its behavior changes dramatically. In experiments published in Nature in 1997, pure sulfur became a superconductor at about 10.1 kelvin, or roughly minus 263°C.

That pressure is the remarkable part. Ninety-three gigapascals is roughly 920,000 times atmospheric pressure at sea level, far beyond anything a conventional machine could produce around a laboratory-sized sample. Researchers created it inside a diamond-anvil cell, a device that uses tiny diamond surfaces to compress matter to extraordinary pressures. The experiment showed that pressure can do much more than squeeze a material—it can change what the material fundamentally is from an electrical point of view.

How Did Scientists Turn Ordinary Sulfur Into a Superconductor?

Superconductivity means that, below a particular critical temperature, a material can carry electrical current without ordinary electrical resistance. Superconductors also interact with magnetic fields in distinctive ways. The phenomenon has been known since 1911, but scientists have spent decades trying to understand why some materials enter this unusual state while others do not.


The sulfur experiment was especially interesting because sulfur started as an insulator and became superconducting after compression. Earlier work had indicated that sulfur would become metallic at pressures near 90 GPa and would undergo another structural change near 160 GPa. The new measurements showed that the first transformation did not simply produce a metal. It produced a superconducting state as well.

The researchers initially observed a critical temperature of about 10 K at 93 GPa. As pressure increased, the superconducting temperature rose gradually. Around 160 GPa, another structural transition produced a much larger change, with the critical temperature reaching about 17 K in the higher-pressure phase. Later measurements extended the pressure range and found a maximum near 17.3 K around 200 GPa before the transition temperature declined at still higher pressures.

How can pressure change an element so much?

The answer lies inside the crystal structure. Pressure forces atoms much closer together, changing how their electrons move and how the atoms vibrate. Those changes can turn an insulating material into a metal and, under the right conditions, allow electrons to enter a superconducting state.

That is why compressed sulfur became more than a curiosity. Scientists could study a relatively simple element while deliberately changing its structure and electronic behavior. The original researchers argued that sulfur could provide a useful test for theories of superconductivity because its chemistry and high-pressure structures were comparatively straightforward to model.

How did researchers detect superconductivity in such a tiny sample?

The team included Viktor Struzhkin, Russell Hemley and Ho-kwang Mao at Carnegie's Geophysical Laboratory and Yuri Timofeev of the Russian Academy of Sciences. Their challenge was enormous: the sulfur sample was microscopic, with dimensions measured in fractions of a millimeter.

Instead of relying only on conventional electrical contacts, the researchers used magnetic susceptibility measurements inside a megabar-capable diamond-anvil cell. That approach allowed them to detect the superconducting transition without attaching electrical leads to the tiny compressed sample. The same experimental strategy was also tested using niobium, a known superconductor, at pressures reaching 132 GPa.

The discovery was made in 1997, so it is not a new laboratory finding today. Its importance becomes clearer when viewed through what followed. High-pressure sulfur research helped establish a broader scientific route toward superconductors created by compression.

The connection became particularly striking years later when researchers found superconductivity at 203 K in a sulfur-hydrogen system under about 150–200 GPa. That material was not pure sulfur—the hydrogen was crucial—but sulfur became part of one of the most important high-pressure superconducting systems ever studied.

Researchers are still using extreme-pressure experiments to probe what happens inside these materials. In 2024, a team including scientists from the National High Magnetic Field Laboratory at Los Alamos National Laboratory used tunneling spectroscopy to examine compressed sulfur at 160 GPa. The work provided microscopic information about its superconducting gap and identified the high-pressure sulfur phase as a type-II superconductor with a single s-wave gap.

Could compressed sulfur ever power American homes?

Not in its compressed elemental form. That distinction matters. Sulfur only becomes superconducting under pressures approaching a million atmospheres, so there is no practical way to put a lump of sulfur into a household electrical system and expect resistance-free power.

The real value is scientific. Researchers can use simple elements under extreme conditions as laboratories for understanding how superconductivity emerges. That knowledge can then guide the search for materials that work at higher temperatures and, ideally, under pressures that are far easier to produce.

For Americans, that could eventually matter in technologies where electrical losses are a major concern, from powerful magnets to specialized electronics and energy systems. But the sulfur experiment itself is not a near-term technology. It is something more fundamental: a demonstration that an ordinary element can acquire extraordinary properties when its atoms are forced into an entirely different environment.

And that may be the most useful lesson from compressed sulfur. The material did not need to be exotic. Scientists simply changed the pressure—and sulfur changed with it.

What is Superconductivity?

Superconductivity is a state where electricity can flow through a material without electrical resistance. In ordinary wires, some energy is lost as heat as electric current moves through them. Superconductors can eliminate this loss when they reach the conditions needed for superconductivity. Scientists study this effect because it could make electrical systems more efficient and powerful.

Researchers are now looking for superconductors that work at higher temperatures and lower pressures. High-pressure materials, including hydrogen-rich compounds, remain important in this search. Scientists are also studying whether similar properties can be reproduced under more practical conditions. The long-term goal is to develop superconducting materials that could work reliably without extreme laboratory pressures.