TUNNELING IN SINGLE-LAYER Bi₂Sr₂CuO_6+\delta SINGLE CRYSTALS IN HIGH MAGNETIC FIELD
Vedeneev S.I., Szabo P., Jansen A.G.M., Vedeneev I.S.

Received: December 25, 2000

PACS: 74.72.Hs, 74.50.+r, 74.25.Jb

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In the tunneling experiments with high-quality single crystals of single-layer cuprate superconductor Bi₂Sr₂CuO_6+δ using the break-junction and point-contact techniques at Tc, the coexistence of the superconducting-state gap and the normal-state gap was observed. The values of the superconducting energy gap 2Δ _p-p are in the range 13.4-15 meV (Δ _p-p=6.7-7.5 meV). The values of 2Δ _p-p are similar for two samples 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 approximately equal to 50 meV, persists at Tc and in the magnetic field up to 28 T. After the transition of the sample to the normal state, the intensity of the tunneling conductance rapidly decreases with increasing magnetic field and temperature. The observed large broadening of the tunneling spectra and large zero-bias conductances can be caused by a strong angular dependence of the superconducting gap. The tunneling results are in full agreement with the angle-resolved photoemission spectroscopy measurements.