Gold gives scientists clues to develop more resilient materials

“Our findings challenge previous understandings by showing that, under certain conditions, metals like gold can become stronger rather than melting when subjected to intense laser pulses,” Adrien Descamps, a researcher at Queen’s University Belfast who led the research while he was a graduate student at Stanford and SLAC, said in a media statement. “This contrasts with semiconductors, which become unstable and melt.”

Descamps explained that for decades, simulations hinted at the possibility of this phenomenon, known as phonon hardening. Now, using SLAC’s Linac Coherent Light Source (LCLS), the researchers have finally brought this phonon hardening to light.

In their experiment, the team targeted thin gold films with optical laser pulses at the Matter in Extreme Conditions experimental hutch, then used super-fast X-ray pulses from LCLS to take atomic-level snapshots of how the material responded. This high-resolution glimpse into the atomic world of gold allowed researchers to observe subtle changes and capture the moment when its phonon energies increased, providing concrete evidence of phonon hardening.

“We used X-ray diffraction at LCLS to measure the structural response of gold to laser excitation,” paper co-author Emma McBride said. “This revealed insights into the atomic arrangements and stability under extreme conditions.”

The researchers found that when gold absorbs extremely high-energy optical laser pulses, the forces holding its atoms together become stronger. This change makes the atoms vibrate faster, which can change how the gold responds to heat and might even affect the temperature at which it melts.

“This work resolves a long-standing question about the ultrafast excitation of metals and shows that intense lasers can completely alternate the response of the lattice,” said Siegfried Glenzer, director of the High Energy Density Division at SLAC.

The scientists believe similar phenomena could exist in other metals such as aluminum, copper, and platinum. Further exploration could lead to a better understanding of how metals behave under extreme conditions, which will aid in the development of more resilient materials.

“Looking ahead, we’re excited about the potential to apply these findings to more practical applications, such as in laser machining and material manufacturing, where understanding these processes at the atomic level could lead to improved techniques and materials,” Descamps said. “We’re also planning more experiments and hoping to explore these phenomena across a wider range of materials.”