Visualizing Critical Correlations Near the Metal-Insulator Transition in Ga1-xMnxAs

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Science  05 Feb 2010:
Vol. 327, Issue 5966, pp. 665-669
DOI: 10.1126/science.1183640

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Electronic states in disordered conductors on the verge of localization are predicted to exhibit critical spatial characteristics indicative of the proximity to a metal-insulator phase transition. We used scanning tunneling microscopy to visualize electronic states in Ga1-xMnxAs samples close to this transition. Our measurements show that doping-induced disorder produces strong spatial variations in the local tunneling conductance across a wide range of energies. Near the Fermi energy, where spectroscopic signatures of electron-electron interaction are the most prominent, the electronic states exhibit a diverging spatial correlation length. Power-law decay of the spatial correlations is accompanied by log-normal distributions of the local density of states and multifractal spatial characteristics.

  • * These authors contributed equally to this work.

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