Energy gaps in failed superconductor La$_{1.875}$Ba$_{0.125}$CuO$_{4}$

By angle-resolved photoemission spectroscopy with improved energy and momentum resolution, we find in the normal state of La$_{2-x}$Ba$_{x}$CuO$_{4}$ x = 1/8 a strong existence of the nodal quasi-particle together with a $d$-wave energy gap along the underlying Fermi surface extending over a significant range in the momentum space before an abrupt take-off of the gap close to the antinodal region. This suggests the presence of a novel nodal metal state, which is different from the one proposed that assumes a single $d$-wave extension of the pseudogap from the antinode toward the node along the whole underlying Fermi surface. This state is compatible with the static stripe ordering but only involves a precursor pairing of the electrons away from the antinodal region. We argue that the traditional pseudogap defined exclusively for the antinodal states has a distinct origin than its new nodal counterpart, i.e., a $d$-wave gap above T$_{c}$. Moreover, this normal state gap function is found to be quantitatively very similar with those of La$_{2-x}$Sr$_{x}$CuO$_{4}$ x$\sim $1/8 (T$_{c}<<$4K) in the superconducting state, pointing to a universal doping dependence of the pairing strength for La-based cuprates, which also highlights the inherent lack of a global phase coherence in La$_{2-x}$Ba$_{x}$CuO$_{4}$ x = 1/8 that makes it a failed superconductor.