Our primary research focuses on understanding properties of exotic superconductors using scanning tunneling microscopy.
Imaging nanoscale Fermi-surface variations in an inhomogeneous superconductor
Having recently reported the presence of checkerboard charge order in Bi-2201 whose average length scale varies with sample doping, we have performed a more in depth investigation of these charge density modulations and found that the length scale of the checkerboard pattern observed in a single sample actually varies dramatically on a ~3 nanometer length scale. These variations are highly correlated with previously reported variations of the local pseudogap magnitude, as pictured above.
Given that these local variations resemble those which, on average, are associated with doping variations between different samples, we hypothesize that the variations are due to local doping (charge density) variations on a nanometer length scale. We find similar results in the related material Bi-2212. In that system, however, we are further able to make use of quasiparticle interference measurements, which have been previously shown to, on average, allow measurement of the Fermi surface. We, for the first time, make these measurements locally, and find that the extracted Fermi surface also varies on the nanometer length scale, consistent with checkerboard-estimated variations. Read more...