Solitons Seen in a Solid

Isolated vibrations within a three-dimensional solid have been observed for the first time by researchers in the U.S. and Germany. The work could help explain how metals such as uranium behave when bent, compressed or heated.

Normally, atoms in a crystal will pass their vibrational energy to their neighbors. But under some circumstances, theory predicts that a small patch of atoms could vibrate in place. This is the first time that these “lattice solitons” have been detected in a three-dimensional solid, said Michael Manley, visiting professor of chemical engineering and materials science at UC Davis and a researcher at the Los Alamos National Laboratory, who is first author on the paper.

The researchers used X-ray and neutron scattering experiments to identify lattice solitons in heated uranium crystals. The results show that the isolated vibrations play an important role in uranium metal, something no one had previously considered, Manley said.

Lattice solitons should actually occur in all kinds of solid materials, but they are very hard to find because they appear and disappear so quickly, Manley said. The significance of the paper is that the researchers were able to see them, he said.

Solitons, or solitary waves, were first described by Scottish scientist John Scott Russell in 1834 after seeing such a wave on a canal. In the late 1980s, scientists theorized that solitons might exist in solids and molecules, calling them intrinsic localized modes or discrete breathers, but had no physical evidence of their existence.

In addition to Manley, the research group included Heather Volz, Jason Lashley, Larry Hults and Jim Smith from Los Alamos; Mohana Yethiraj from Oak Ridge National Laboratory; Harald Sinn and Ahmet Alatas from Argonne National Laboratory; and Gerry Lander from Institute for Transuranium Elements in Karlsruhe, Germany. The research is published in Physical Review Letters.