Towards an understanding of the cuprates- some recent quantum oscillation
experiments at the National High Magnetic Field Laboratory
John Singleton, National High Magnetic Field Laboratory, TA-35, MS-E536,
Los Alamos National Laboratory, Los Alamos, NM 87545, USA
Pulsed magnetic fields of up to 85 T and temperatures down to 0.40 K have been used to
study single crystals of various cuprate superconductors. The samples are measured using
a MHz technique that is sensitive to small changes in penetration depth in the
superconducting state, and to changes in the skin depth in the normal state. In the normal
state, clear magnetic quantum oscillations are observed, periodic in inverse field. The
observed frequencies are low (e.g. in YBa2Cu4O8, the frequency is 660±15 T) suggesting
that the predicted large Fermi surface is broken into smaller pockets due to nesting. The
temperature dependence of the oscillations also reveals the quasiparticle masses for the
various compounds. Taken in conjunction with the results of Doiron-Leyraud et al. for
YBa2Cu3O6.5, our data reveal some general features of the bandstructure of the cuprates
and provide information about the doping dependence of the Fermi surface.
Magnetic quantum oscillations are generally recognized to be the most reliable
method for deducing the Fermi-surface topology of metals. It is therefore instructive to
consider how such data can be reconciled with the results of techniques such as ARPES.
By considering the effect of a short antiferromagnetic correlation length on the
electronic bandstructure and a Fermi-surface topology consistent with the magnetic-
quantum-oscillation experiments, it can be shown that a reduced gives an asymmetric
broadening of the quasiparticle dispersion, resulting in simulated ARPES data very
similar to those observed in experiment. Predicted features include the presence of
“Fermi arcs” close to ak = ( /2, /2), where a is the in-plane lattice parameter, without
the need to invoke a d-wave pseudogap order parameter. The statistical variation in the k-
space areas of the reconstructed Fermi-surface pockets causes the quantum oscillations to
be strongly damped, even in very strong magnetic fields, in agreement with experiment.

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