The enhanced s*-wave component of the superconducting gap in the overdoped HTSC cuprates with orthorhombic distortion

In this work, the concentration and temperature dependences of the superconducting gap of the HTSC cuprate in the orthorhombic phase are obtained within the framework of the Hubbard model taking into account the exchange mechanism of pairing. The enhanced s*-wave component of the superconducting gap against the background of the prevailing d-wave component in a narrow range of hole concentrations in the overdoped region is found. To elucidate the reasons for such unusual behavior the electronic structure of the low-energy excitations and the structure of the contributions of the pair states to the superconducting gap in momentum space were investigated at different doping. It is shown that the presence of a shallow pocket in the region of the maximum value of the s*-wave component of the gap results in different symmetry of the superconducting gap in different regions of the k-space and an increase in the s*-wave component.
Comment: 17 pages, 11 figures