I have been working through a really nice paper, Fermi surface of the electron-doped cuprate superconductor Nd2–xCexCuO4 probed by high-field magnetotransport by Mark Kartsovnik and collaborators.
The phase diagram of these electron-doped [in contrast to the more common hole-doped cuprates] materials is shown below. x is the Ce content. PG denotes a pseudogap phase.
(b) Shows the Fermi surface expected for x > 0.16 (e.g. from a tight binding model and DFT based calculations) and confirmed by Shubnikov de Haas (SdH) oscillations.
(c) shows how this Fermi surface may be re-constructed due to a (pi,pi) superlattice potential (which might exist due to co-existing antiferromagnetic (AF) order.
I found the interlayer magnetoresistance measurements shown below particularly interesting. Each curve shows the interlayer resistivity as a function of magnetic field direction (theta= tilt angle from the normal to the layers) for a fixed magnetic field and temperature.
[Above some large angle the resistance goes to zero because the component of magnetic field perpendicular to the layers becomes less than the upper critical field needed to destroy the superconductivity].
- They exhibit significant qualitative differences depending on the doping x, even over the narrow range 0.13 < x < 0.17.
- This is probably because the pseudogap has a big effect on the magnetoresistance.
- For x=0.13, 0.15 the dependence on the azimuthal direction (phi) of the magnetic field is very weak (and opposite in sign) compared to that for x=0.16, 0.17.