Fingerprint of dynamical spin-charge correlations in the tunneling spectra of colossal magnetoresistive manganites

Abstract

We present temperature-dependent scanning tunneling spectroscopy measurements on La1-x Cax MnO3 (x∼0.33) films with different degrees of biaxial strain. A depletion in normalized conductance around the Fermi level is observed both above and below the insulator-to-metal transition temperature TMI, for weakly as well as highly strained films. This pseudogaplike depletion globally narrows on cooling. The zero-bias conductance decreases on cooling in the insulating phase, reaches a minimum close to TMI and increases on cooling in the metallic phase, following the trend of macroscopic conductivity. These results support a recently proposed scenario in which dynamical short-range antiferromagnetic/charge order correlations play a preeminent role in the transport properties of colossal magnetoresistive manganites. © 2009 The American Physical Society.