Manifestations of broken symmetry: the surface phases of Ca(2-x)SrxRuO4

Phys Rev Lett. 2008 Feb 15;100(6):066102. doi: 10.1103/PhysRevLett.100.066102. Epub 2008 Feb 13.


The surface structural phases of Ca(2-x)SrxRuO4 are investigated using quantitative low energy electron diffraction. The broken symmetry at the surface enhances the structural instability against the RuO6 rotational distortion while diminishing the instability against the RuO6 tilt distortion occurring within the bulk crystal. As a result, suppressed structural and electronic surface phase transition temperatures are observed, including the appearance of an inherent Mott metal-to-insulator transition for x=0.1 and possible modifications of the surface quantum critical point near x(c) approximately 0.5.