Researchers at SLAC’s Matter in Extreme Conditions (MEC) instrument used a laser to superheat a sample of gold. Then, they sent a pulse of ultrabright X-rays from the Linac Coherent Light Source (LCLS) through the sample to measure the speed, and thus the temperature, of the atoms vibrating in the sample. Credit: Greg Stewart/SLAC National Accelerator Laboratory
Researchers heated gold to unprecedented temperatures without melting it, overturning a century-old theory and paving the way for breakthroughs in fusion and planetary science.
Record-Breaking Heat and Shattered Theories
Scientists have achieved a remarkable feat, setting a new temperature record, challenging a long-accepted theory, and applying an advanced laser spectroscopy technique to dense plasmas. Their findings were recently published in Nature.
In the study, titled “Superheating gold beyond the predicted entropy catastrophe threshold,” researchers reported that they were able to heat gold to more than 19,000 Kelvin (33,740 degrees Fahrenheit). This is over 14 times its normal melting point, yet the gold astonishingly retained its solid, crystalline form.
“This is possibly the hottest crystalline material ever recorded,” Thomas White, lead author and Clemons-Magee Endowed Professor in Physics at the University of Nevada, Reno, said.
Defying the Entropy Catastrophe
The experiment directly challenges the long-standing theory known as the entropy catastrophe. According to this theory, solids cannot remain intact at temperatures greater than about three times their melting point and should instead melt on their own. Gold’s melting point is 1,337 Kelvin (1,947 degrees Fahrenheit), yet in this experiment at Stanford University’s SLAC National Accelerator Laboratory, the metal remained solid far beyond that threshold when blasted with a powerful laser.
“I was expecting the gold to heat quite significantly before melting, but I wasn’t expecting a fourteen-fold temperature increase,” White said.
Lightning-Fast Laser Experiment
To heat the gold, researchers at the University of Nevada, Reno, SLAC National Accelerator Laboratory, the University of Oxford, Queen’s University Belfast, the European XFEL, and the University of Warwick designed an experiment to heat a thin gold foil using a laser fired for 50 quadrillionths of a second (one millionth of a billionth). The speed with which the gold was heated seems to be the reason the gold remained solid.
The findings suggest that the limit of superheating solids may be far higher – or nonexistent – if heating occurs quickly enough. The new methods used in this study open the field of high-energy density physics to further exploration, including in areas of planetary physics and fusion energy research.
White and his team expected that the gold would melt at its melting point, but to measure the temperature inside the gold foil, they would need a very special thermometer.
“We used the Linac Coherent Light Source, a 3-kilometer-long X-ray laser at SLAC, as essentially the world’s largest thermometer,” White said. “This allowed us to measure the temperature inside the dense plasma for the first time, something that hasn’t been possible before.”
“I’m incredibly grateful for the opportunity to contribute to such cutting-edge science using billion-dollar experimental platforms alongside world-class collaborators.”
Doctoral student Travis Griffin
Fusion Research Potential
“This development paves the way for temperature diagnostics across a broad range of high-energy-density environments,” Bob Nagler, staff scientist at SLAC and coauthor on the paper, said. “In particular, it offers the only direct method currently available for probing the temperature of warm dense states encountered during the implosion phase of inertial fusion energy experiments. As such, it is poised to make a transformative contribution to our understanding and control of fusion-relevant plasma conditions.”
Along with the experimental designers, the research article is the result of a decade of work and collaboration between Columbia University, Princeton University, the University of Padova and the University of California, Merced.
“It’s extremely exciting to have these results out in the world, and I’m really looking forward to seeing what strides we can make in the field with these new methods,” White said.
Expanding High-Energy Physics Frontiers
The research, funded by the National Nuclear Security Administration, will open new doors in studies of superheated materials.
“The National Nuclear Security Administrations’ Academics Program is a proud supporter of the groundbreaking innovation and continued learning that Dr. White and his team are leading for furthering future critical research areas beneficial to the Nuclear Security Enterprise,” Jahleel Hudson, director at the Techology and Partnerships Office of the NNSA said.
Probing Planetary Interiors
White and his colleagues returned to the Linac Coherent Light Source in July to measure the temperature inside hot compressed iron and are using those results to gain insights into the interiors of planets.
Several of White’s graduate students and one undergraduate student were coauthors on the study, including doctoral student Travis Griffin, undergraduate student Hunter Stramel, Daniel Haden, a former postdoctoral scholar in White’s lab, Jacob Molina, a former undergraduate student currently pursuing his doctoral degree at Princeton University and Landon Morrison, a former undergraduate student pursuing his master’s degree at the University of Oxford. Jeremy Iratcabal, research assistant professor in the Department of Physics, was also a coauthor on the paper.
“I’m incredibly grateful for the opportunity to contribute to such cutting-edge science using billion-dollar experimental platforms alongside world-class collaborators,” Griffin said. “This discovery highlights the power of this technique, and I’m excited by the possibilities it opens for the future of high-energy-density physics and fusion research. After graduation, I’ll be continuing this work as a staff scientist at the European XFEL.”
Reference: “Superheating gold beyond the predicted entropy catastrophe threshold” by Thomas G. White, Travis D. Griffin, Daniel Haden, Hae Ja Lee, Eric Galtier, Eric Cunningham, Dimitri Khaghani, Adrien Descamps, Lennart Wollenweber, Ben Armentrout, Carson Convery, Karen Appel, Luke B. Fletcher, Sebastian Goede, J. B. Hastings, Jeremy Iratcabal, Emma E. McBride, Jacob Molina, Giulio Monaco, Landon Morrison, Hunter Stramel, Sameen Yunus, Ulf Zastrau, Siegfried H. Glenzer, Gianluca Gregori, Dirk O. Gericke and Bob Nagler, 23 July 2025, Nature.
DOI: 10.1038/s41586-025-09253-y
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