Electronic Surface Melting

February 13, 2012

The performance of devices like transistors and memory chips depends on controlling the behavior of electrons at surfaces and interfaces of complex structures.  Using surface X-ray scattering techniques, researchers at Brookhaven and Argonne National Laboratories have shown that ensembles of electrons in certain oxide compounds “freeze” and “melt” in ways analogous to the freezing/melting of ordinary ice.

Upon heating, the surface of crystalline ice melts before the bulk, a phenomenon that allows skiers to glide across snow.  What if electrons are the elements of the crystal lattice instead of water molecules?  They, too, can freeze into ordered arrays at very low temperatures.  The researchers studied such frozen electronic order at the surface of an oxide material kept just below the temperature at which it would begin to melt in the bulk. They found that the electronic surface pre-melted, while the bulk remained frozen, establishing electronic surface melting. This result has important implications for future electronic devices that require well-defined electronic interfaces, and particularly for nanoscaled devices, whose performance is dominated by their surface electronic behavior.

An account of the work appeared in the 15 October 15, 2011, issue of Physical Review B, where it is an Editor’s Suggestion: S. B. Wilkins et al., Phys. Rev. B. 84 165103 (2011).