Scanning tunneling spectroscopy across the insulator-to-metal transition in La0.67Ca0.33MnO3 thin films

We present the temperature evolution of scanning tunneling spectra of La0.67Ca0.33MnO3 thin films across the insulator-to-metal transition. A depletion in normalized conductance is observed over an energy range of a few hundred meV around the Fermi level. This depletion globally narrows upon cooling but is still present in the metallic phase. The link to macroscopic transport behavior is provided by the tunnel conductance at zero bias, which decreases upon cooling in the insulating phase, reaches a minimum close to the insulator-to-metal transition temperature and increases on cooling in the metallic phase. These results are interpreted in terms of dynamical short-range antiferromagnetic/charge order correlations.