Materials Science

Coming to Order

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Science  02 Sep 2011:
Vol. 333, Issue 6047, pp. 1202
DOI: 10.1126/science.333.6047.1202-b

That cuprate superconductors are perfect conductors up to such high transition temperatures (Tc) is all the more surprising in light of their origin as chemically doped insulators. In some layered cuprate families, such as La2CuO4+y, ordered oxygen dopants that intercalate between the CuO2 layers are used to elicit superconductivity. When first introduced, however, these oxygen ions are mobile and disordered. Ordering takes place on a time scale of weeks, and little is known about the details of this process. Poccia et al. fast-forward the ordering dynamics by illuminating a disordered sample with x-rays, and use x-ray diffraction (XRD) to monitor the evolution of order, both parallel (a and b axes) and perpendicular (c axis) to the CuO2 layers. The XRD data reveal that the initial sample has small (∼2 nm), almost isotropic islands of order, which act as nuclei for the final ordered state: They initially combine, then grow predominantly in the a-b plane, and finally along the c axis. The authors use the x-ray switching to create simple patterns (a dot and a line) of order in a disordered sample, which can be erased by heating. Because Tc is found to grow with ordering, it is in principle possible to create more complicated circuits as well.

Nat. Mater. 10, 10.1038/NMAT3088 (2011).

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