title: Small Fermi surface pockets in underdoped high temperature superconductors: observation of Shubnikov-de Haas oscillations in YBa2Cu4O8.
abstract: We report the observation of Shubnikov-de Haas oscillations in the underdoped cuprate superconductor YBa2Cu4O8 (Y124). For fields aligned along the c axis, the frequency of the oscillations is 660+/-30 T, which corresponds to approximately 2.4% of the total area of the first Brillouin zone. The effective mass of the quasiparticles on this orbit is measured to be 2.7+/-0.3 times the free electron mass. Both the frequency and mass are comparable to those recently observed for ortho-II YBa2Cu3O6.5 (Y123-II). We show that although small Fermi surface pockets may be expected from band-structure calculations in Y123-II, no such pockets are predicted for Y124. Our results therefore imply that these small pockets are a generic feature of the copper oxide plane in underdoped cuprates.
authors: H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, BS8 1TL, United Kingdom.
authors: A F
authors: AF
authors: Bangura
authors: J D
authors: JD
authors: Fletcher
authors: A
authors: A
authors: Carrington
authors: J
authors: J
authors: Levallois
authors: M
authors: M
authors: Nardone
authors: B
authors: B
authors: Vignolle
authors: P J
authors: PJ
authors: Heard
authors: N
authors: N
authors: Doiron-Leyraud
authors: D
authors: D
authors: Leboeuf
authors: L
authors: L
authors: Taillefer
authors: S
authors: S
authors: Adachi
authors: C
authors: C
authors: Proust
authors: N E
authors: NE
authors: Hussey