LAYERED MODELS AND TUNNELING IN HTSC

Tunneling current-voltage characteristics of the structures ''Normal m etal-Isolator-HTSC'' (NIS-structure) and ''HTSC-Isolator-HTSC'' (SIS-s tructure) are analyzed for the layered model of a high temperature sup erconductor (HTSC). The contributions of the superconducting and norma l layers of HTSC to the tunneling current of NIS- and SIS-structures w as found. There are three and eight peculiarities on the theoretical I (V)-characteristics for NIS- and SIS-structures, correspondingly, whic h are connected with singularities in the density of states of HTSC. C omparison is given with experimental data on tunneling in HTSC. The po ssibility to explain the experimental results (particularly, ''knee'' structure) by effects of density of states in HTSC on current-voltage characteristics is discussed.