Pseudogap behavior in Pr_0.5Sr_0.5MnO₃: A photoemission study

The valence band electronic structure of Pr0.5Sr0.5MnO3 has been investigated across its paramagnetic metallic (PMM)-ferromagnetic metallic (FMM)-antiferromagnetic insulator (AFMI) transition. Using surface sensitive high resolution photoemission we have conclusively demonstrated the presence of a pseudogap of magnitude 80 meV in the near Fermi level electronic spectrum in the PMM and FMM phases and finite intensity at the Fermi level in the charge ordering (CO)-AFMI phase. The pseudogap behavior is explained in terms of the strong electron-phonon interaction and the formation of Jahn Teller UT) polarons, indicating the charge localizations. The finite intensity at the Fermi level in the insulating phase showed a lack of charge ordering in the surface of the Pr0.5Sr0.5MnO3 samples