Spin Zeros and the Origin of Fermi Surface Reconstruction in the Cuprates

Two recent quantum oscillation studies find contradictory results concerning the existence of spin zeros - zeros of the oscillatory signal induced by Zeeman splitting of the Landau levels. We discuss these experiments in light of calculations of the oscillations assuming a spin density wave state. We find that the lack of spin zeros reported in one of the experiments is consistent with either hole or electron pockets in such a state, if the staggered moment is perpendicular to the external field. An analysis for field directions near the planes might be able to differentiate between the two. On the other hand, if spin zeros exist as reported in the other experiment, then the staggered moment would have to have a substantial longitudinal component. We suggest several experiments to test whether this is indeed the case.