Mapping out the pseudogap with interlayer magnetoresistance

Given the success described in the prevous post, an important question I have been wondering about the last couple of years is whether angle-dependent magnetoresistance (ADMR) can be used to detect and quantify the anisotropy of a pseudogap? I believe the answer is yes, based on recent calculations by Michael Smith, described in this preprint. Michael and I derived an expression for the interlayer magnetoresistance as a function of the direction of the tilted field, including the effects of anisotropies in all Fermi surface quantities including the pseudogap. We found a pseudogap can have significant effects on ADMR. As the temperature decreases the interlayer conductivity is dominated by the parts of the Fermi surface near the nodes of the pseudogap. This reduces the amplitude of variation in the magnetoresistance as the direction of the component of the field parallel to the layers changes. As the magnitude of the pseudogap increases the anisotropy becomes dominated by the anisotropy of the pseudogap rather than by the anisotropy of the intralayer Fermi velocity. This is illustrated in the Figure below which is a polar plot of the magnitude of the interlayer resistivity (for a band structure similar to that of overdoped Tl2201) as a function of the direction of the field parallel to the layers.

Our results should make it possible to determine the magnitude and anisotropy of the pseudogap in overdoped cuprates. This could answer outstanding questions about the pseudogap and the cuprate phase diagram that I described in a previous post.

There is some experimental evidence for a pseudogap in some organic charge transfer salts, the new iron pnictide superconductors , electron doped cuprates, and the layered heavy fermion compounds CeMIn5 [M=Co, Rh, Ir]. Hopefully, this work will stimulate more experimentalists to use this powerful probe of intralayer Fermi surface anisotropies.