In a remarkable scientific breakthrough, researchers have successfully heated gold to an astonishing 19,000 kelvins (approximately 33,700 degrees Fahrenheit), which is 14 times its normal melting point, without the metal transitioning into a liquid state. This groundbreaking achievement, detailed in the journal Nature, directly challenges a long-held theory from the 1980s concerning the limits of solid superheating.
The experiment, led by Bob Nagler at the SLAC National Accelerator Laboratory, utilized ultrafast X-ray laser pulses to rapidly heat a thin gold film. The core of this discovery lies in the unprecedented speed of the heating process. By bombarding the gold film with 45-femtosecond X-ray laser pulses, the atoms within the crystalline structure vibrated at a frequency directly correlated with their rapidly increasing temperature. This rapid energy transfer prevented the gold's atomic lattice from destabilizing and collapsing, thereby maintaining its solid form even at these extreme temperatures. This phenomenon sidesteps the classical understanding of the "entropy catastrophe," a theoretical limit suggesting that solids must melt when heated beyond approximately three times their melting point to avoid violating the second law of thermodynamics.
This advancement offers a novel method for measuring extreme temperatures, a long-standing challenge in materials science. Previously, accurately gauging the temperature of transient states of matter, known as warm dense matter, was difficult due to their fleeting nature. The technique employed in this study, which involves analyzing the scattering of X-rays off vibrating atoms, provides a direct and precise way to determine temperature, offering significant implications for understanding exotic matter states found in environments like the cores of planets and the interiors of stars.
The ability to maintain a solid state at such elevated temperatures, even for picoseconds, has profound implications. It suggests that the established boundaries of material behavior under extreme thermal stress may be more flexible than previously understood. This could revolutionize fields ranging from astrophysics, where understanding stellar interiors is key, to the development of materials for advanced technological applications. The research team, which included scientists from institutions such as the University of Nevada, Reno, and Queen's University Belfast, is exploring whether other materials might exhibit similar behavior under rapid heating conditions. This discovery not only pushes the boundaries of our understanding of physics but also opens new avenues for scientific inquiry into the fundamental properties of matter under extreme conditions.