Tunneling in single-layer Bi2Sr2CuO6+delta single crystals in high magnetic field

In tunneling experiments with high-quality single crystals of a single-laye r cuprate superconductor Bi2Sr2CuO6+delta using the break junction and poin t-contact techniques at T < T-c, the coexistence of the superconducting-sta te gap and the normal-stare gap was observed. The values of the superconduc ting energy gap 2<Delta>(p-p) are in the range from 13.4 to 15 meV (Delta ( p-p) = 6.7-7.5 meV). The values of 2 Delta (p-p) are similar for two sample s with T-c = 4 K and for two samples with T-c = 9-10 K and are independent of the carrier concentration. The normal-state gap, with the magnitude appr oximately equal to 50 meV, persists at T < T-c and in the magnetic field H >> H-c2 up to 28 T. After the transition of the sample to the normal state, the intensity of the tunneling conductance rapidly decreases with increasi ng magnetic field strength and temperature. The observed large broadening o f the tunneling spectra and large zero-bias conductances can be caused by a strong angular dependence of the superconducting gap. The tunneling result s are in full agreement with the data of the angle-resolved photoemission s pectroscopy measurements. (C) 2001 MAIK "Nauka/Interperiodica".