Tunneling measurements of the energy gap in Bi 4 Ca 3 Sr 3 Cu 4 O 1 6 + δ

We have measured at 4.2 and 53 K the tunneling current-voltage ($I\ensuremath{-}V$) characteristics of the new high-${T}_{c}$ superconductor ${\mathrm{Bi}}_{4}{\mathrm{Ca}}_{3}{\mathrm{Sr}}_{3}{\mathrm{Cu}}_{4}{\mathrm{O}}_{16+\ensuremath{\delta}}$ with $\ensuremath{\delta}=0.32$, using a low-temperature scanning-tunneling microscope. We obtain gap values $\ensuremath{\Delta}$ ranging between 15 and 23 meV. This corresponds to $\frac{2\ensuremath{\Delta}}{{K}_{B}{T}_{c}}$ values between 4.5 and 6.5. These results are consistent with strong-coupling superconductivity. A study of the spatial dependence of $\ensuremath{\Delta}$ has been done at 4.2 K.