Researchers at SLAC National Accelerator Laboratory and the University of Nevada, Reno, have managed to heat a nanometer-thick gold sample to 19,000 kelvins—over 14 times its melting point—using an ultrafast laser pulse lasting just 45 femtoseconds. Despite the extreme temperature, the gold remained solid, overturning decades-old predictions about molten limits Interesting Engineering+5.
How It Was Done
- Flash heating: A high-powered laser delivered an intense burst of energy so quickly there was no time for the metal to expand and melt
- X-ray thermometer: SLAC’s Linac Coherent Light Source (LCLS) fired ultrabright X-rays at the sample. By measuring X-ray scattering shifts, researchers could directly gauge atomic motion and temperature
Breaking the “Entropy Catastrophe” Limit
For nearly 40 years, physicists believed that at a certain temperature solids would collapse under entropy pressure—a theory known as the “entropy catastrophe.” This experiment shows solids can withstand far greater heat if exposure is ultrafast, maintaining structure due to insufficient time for melting processes
Why This Matters
- New measurement technique: Direct atom-temperature readings offer vital data for studying warm dense matter, found in planetary cores or fusion reactors
- Fusion research: Understanding extreme-state materials aids in modeling fusion processes and designing next-gen reactors
- Revising material physics: Challenges long-held thermodynamic boundaries, prompting revision of existing high-temperature material models.
Next Steps and Open Questions
The researchers plan to extend this method to other materials—like iron—to better simulate conditions inside planets or in fusion environments
However, experts caution that these results apply under ultrafast, nanoscale conditions. The behavior of regularly heated, larger samples may differ and requires further investigation
Bottom Line
Gold’s ability to withstand 19,000 kelvins without melting marks a pivotal moment in high-temperature physics. Thanks to flash heating and direct atomic thermometry, this result reshapes our understanding of solid-state limits and opens new opportunities in fusion science and extreme-matter research.
