Gap and subgap tunnelling in cuprates

We describe strongly attractive carriers in cuprates in the framework of a simple quasi one-dimensional Hamiltonian with a local attraction. In contrast with the conventional BCS theory, there are two energy scales, a temperature-independent incoherent gap Delta (p) and a temperature-dependent coherent gap Delta (c) (T) combining into one temperature-dependent global gap Delta = (Delta (2)(p) + Delta (2)(c))(1/2). The temperature dependence of the gap and single-particle (Giaver) tunnelling spectra in cuprates are quantitatively described. Two distinct energy scales observed in Giaver tunnelling and electron-hole reflection experiments are understood and their link with the zero-bias conductance peak and the symmetry of the order parameter is discussed.