X-rays Reveal Spin Waves in a Single La2CuO4 Layer
The basic building blocks of the high temperature superconductors are two dimensional (2D) magnetic copper oxide layers. The magnetic response of three dimensional (3D) crystals, composed of interacting stacks of these layers, has been intensely studied for many years, but the response of a single copper oxide layer remained unknown. Now, scientists at Brookhaven National Laboratory have grown isolated 2D layers of lanthanum copper oxide (La2CuO4) and used x-ray scattering to probe their magnetic response.
When a spin is tipped in a magnet, its neighbors follow suit and the disturbance propagates through the sample as a "spin wave." These spin waves may be what bind electrons together to create high-temperature superconductivity. Surprisingly, these experiments revealed that 2D copper-oxide layers host spin waves similar to those in 3D materials. Predicted quantum superposition correlations were found not present in the 2D layers, although a high energy magnetic continuum cannot be explained by the standard classical spin wave theory.
This work helps us understand the magnetic response of nanostructured, superconducting materials - something that is vital for future commercial applications.
This work was published online on 02 September 2012 in Nature Materials: M. P. M. Dean, R. S. Springell, C. Monney, K. J. Zhou, J. Pereiro, I. Bozovic, B. Dalla Piazza, H. M. Ronnow, E. Morenzoni, J. van den Brink, T. Schmitt, and J. P. Hill, Nature Materials DOI 10:1038 (2012).
This work was supported by the U.S. Department of Energy Office of Science.