Colossal magnetoresistive (CMR) manganites are prototypical strongly correlated materials which have attracted a lot of attention since they exhibit the colossal magnetosistive effect, i.e. the large increase of electrical conductivity upon application of a magnetic field.

In this talk, I will discuss the results of some recent angle-resolved photoemission spectroscopy (ARPES) investigations which allowed elucidating the controversial nature of the ferromagnetic metallic groundstate in the prototypical CMR bilayer compound La1.2Sr1.8Mn2O7 [i]. The distribution of spectral weight in momentum space exhibits a nodal-antinodal dichotomous character. Quasiparticle excitations have been detected for the first time along the nodal direction (i.e. diagonal), and they are found to determine the metallic transport properties of this compound. These nodal quasiparticles coexist with strong anisotropic electron-boson interactions. The weight of the quasiparticle peak diminishes rapidly while crossing over to the antinodal (i.e. parallel to the Mn-O bonds) parallel sections of the Fermi surface. In particular, the spectra along the antinodal straight sections of the Fermi surface strongly resemble those found in heavily underdoped cuprates high temperature superconductors such as Ca2-xNaxCuO2Cl2 [ii].

This dichotomy between the electronic excitations along the nodal (diagonal) and antinodal (parallel to the Cu-O bonds) directions in momentum space was so far considered a characteristic unique feature of the copper oxide high-temperature superconductors (HTSC). These findings therefore cast doubt on the assumption that the pseudogap state and the nodal-antinodal dichotomy in the copper oxides HTSC are hallmarks of the superconductivity state.