Quantum oscillations in the underdoped cuprate YBa2Cu4O8

We report the observation of quantum oscillations in the underdoped cuprate superconductor YBa(2)Cu(4)O(8) using a tunnel-diode oscillator technique in pulsed magnetic fields up to 85 T. There is a clear signal, periodic in inverse field, with frequency 660 +/- 15 T and possible evidence for the presence of two components of slightly different frequency. The quasiparticle mass is m*=3.0 +/- 0.3m(e). In conjunction with the results of Doiron-Leyraud et al. for YBa(2)Cu(3)O(6.5), the present measurements suggest that Fermi surface pockets are a general feature of underdoped copper oxide planes and provide information about the doping dependence of the Fermi surface.