X-rays reveal surprisingly long-lived spin waves in copper oxide

Copper oxide, a well-known magnetic material, has been studied by a research team at the Paul Scherrer Institute (PSI) using X-ray techniques. The team aimed to understand the dynamics of spin waves, or magnons, in the material. Spin waves are collective excitations of electron spins, which could potentially be used in ultrafast logic components like transistors, leading to more efficient and faster computer technology.

The researchers chose copper oxide due to its strong interactions between magnetism and lattice vibrations, known as phonons.

Using a combination of X-ray techniques, including pump-probe methods and time-resolved resonant diffuse scattering, the team was able to capture the rapid interplay among different excitations in the material. They first excited the electrons in the material with an intense, short optical laser pulse. This caused the initially disordered spins to flip in rows, generating magnons within femtoseconds (quadrillionths of a second).

The magnons then scattered off each other and formed incoherent waves over picoseconds (trillionths of a second). After three orders of magnitude, or nanoseconds (billionths of a second), the magnons interacted with the atoms in the crystal lattice and converted their energy into phonons, leading to the eventual decay of the magnons.

The team found that the magnons have a surprisingly long lifetime before they convert into phonons. This extended lifetime could allow for the performance and control of logical operations, potentially leading to the development of more efficient and faster computer technology. The study, published in Nature Communications, provides valuable insights into the behavior of spin waves in copper oxide and the potential for using specifically designed materials to control the lifetime of magnons.