Superconductivity, pseudo-gap, and stripe correlations in high-T_c cuprates

Under-doped La-214 cuprates show a charge- and spin-modulation known as “stripes” [1]. These stripe modulations are (quasi)-static close to 1/8 hole doping where superconductivity is suppressed. The pseudo-gap phase of other cuprate compounds recently also revealed charge modulation, but interpreted rather as a charge density wave (CDW) [2–4], that possibly competes with superconductivity. In this context, to better understand the interplay between the stripe phase and the superconductivity, we use angle-resolved photoemission spectroscopy to study the electronic band structure and gap in La-214 cuprates near 1/8 doping (La_2−x−yNd_ySr_xCuO₄ (x = 0.12; y = 0.0 & 0.4)) and compare with the previous results in the same system [5] and La_1.86Ba_0.14CuO₄ [6]. Our data shows a loss of spectral intensity towards the end of the Fermi arcs, that is possibly due to a strong renormalisation, as already pointed out elsewhere [6], with a noisy but still measurable gap. On the nodal direction no gap is observed within our statistics, but a sizeable decrease in intensity with temperature. Moreover, we do not see any shadow band, but our Fermi surface can be well modelled with a single electron band calculation in the tight binding approximation, even very close to the 1/8 doping La_2−x−yNd_ySr_xCuO₄ with and without Nd substitution.