Physics

Unexpected Conductivity

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Science  14 Jun 2013:
Vol. 340, Issue 6138, pp. 1267
DOI: 10.1126/science.340.6138.1267-b

Interfacing two dissimilar crystals can lead to unexpected phenomena, as best illustrated by the formation of a highly mobile metallic two-dimensional electron gas (2DEG) between two insulators, SrTiO3 (STO) and LaAlO3. The interface is usually formed using the (100) crystallographic orientation of the substrate, STO, and the conductivity of the 2DEG is explained through the polarization catastrophe model, in which the discontinuity of the polarization at the interface leads to charge transfer. Annadi et al. studied what happens when the (110)-oriented STO is used as a substrate instead. Naïvely, one may expect that in this case the interface would always be insulating, because there is no polarization discontinuity; however, the researchers found that the transport properties of such interfaces are similar to those formed on (100) surfaces. One exception to that similarity was the appearance of anisotropic conductivity, attributed to the differing properties of the Ti-O-Ti chains along the two in-plane directions. First-principles calculations suggested that the unexpected conductivity could be explained through the model of an energetically stable buckled interface, which, contrary to expectations, did induce a polarization discontinuity.

CREDIT: A. DEMOGINES ET AL., PLOS BIOLOGY 11, 5 (28 MAY 2013)

Nat. Comm. 4, 1838 (2013).

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