The deviation in the d-wave behaviour of the gaps in Cuprate high-temperature superconductors

► Data on the dispersion of the pseudogap in one layer CHTSC are compiled. ► There are two pseudogaps in the one layer CHTSC. ► In addition to the two pseudogaps there is a superconducting gap in the CHTSC. ► It is concluded that superconductivity and competing order exist in parallel in the CHTSC. The (Cuprate) High Temperature Superconductors (CHTSCs) are characterised by a d-wave gap of the cos(2ϕ) form. In some systems, deviations from this canonical behaviour are observed in ARPES experiments. In this note ARPES experiments on the gaps of the one layer systems Bi2201 and LSCO are inspected and analysed. The available data give for optimal doping a superconducting gap of (9±2) meV, and a pseudogap, which originates from the preformed pairs, of (15±3) meV. A second pseudogap, (35±5) meV, with a shorter wave vector is observed in many experiments and is ascribed to an additional ordered structure. The existence of the two pseudogaps is responsible for the deviation from the canonical cos(2ϕ) behaviour. Thus the question whether the pseudogap observed in the CHTSC by ARPES is due to preformed pairs or due to additional order does not really exist at least in the one layer compounds. There are two pseudogaps present in the one layer CHTSC, one due to preformed pairs, which become superconducting below Tc, and a second one, reflecting an additional order, which is most likely the checkerboard structure.