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The asymmetric Fermi surface of Bi2201

by Steef Smit, Kourosh Lwydd Shirkoohi, Saumya Mukherjee, Sergio Barquero Pierantoni, Lewis Bawden, Erik van Heumen, Arnaud Pastel Nono Tchiomo, Jans Henke, Jasper van Wezel, Ying Kai Huang, Takeshi Kondo, Tsunehiro Takeuchi, Timur K. Kim, Cephise Cacho, Marta Zonno, Sergey Gorovikov, Stephen Brian Dugdale, Jorge Ismael Facio, Mariia Roslova, Laura Folkers, Anna Isaeva, Nigel Edward Hussey, Mark Stephen Golden

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Authors (as registered SciPost users):

Kourosh Lwydd Shirkoohi

Abstract

High-resolution angle-resolved photoemission spectroscopy (ARPES) performed on the single-layered cuprate (Pb_(y),Bi_(1-y))_(2)Sr_(2−x) La_(x)CuO_(6+δ), or Bi2201, reveals a 6-10% difference in the nodal kF vectors along the GY and GX directions. This asymmetry is notably larger than the 2% orthorhombic distortion in the CuO2 plane lattice constants determined using X-ray crystallography from the same samples. First principles calculations indicate that crystal-field splitting of the bands lies at the root of the kF asymmetry. Concomitantly, the nodal Fermi velocities for the GY quadrant exceed those for GX by 4%. Momentum distribution curve widths for the two nodal dispersions are also anisotropic, showing identical energy dependencies, bar a scaling factor of ~ 1.17±~0.05 between GY and GX. Consequently, the imaginary part of the self-energy is found to be 10-20% greater along GY than GX. These results emphasize the need to account for Fermi surface asymmetry in the analysis of ARPES data on Bi-based cuprate high temperature superconductors such as Bi2201. To illustrate this point, an orthorhombic tight-binding model (with twofold in-plane symmetry) was used to fit ARPES Fermi surface maps spanning all four quadrants of the Brillouin zone, and the ARPES-derived hole-doping (Luttinger count) was extracted. Comparison of the Luttinger count with one assuming four-fold in-plane symmetry strongly suggests the marked spread in previously-reported Fermi surface areas from ARPES on Bi2201 results from the differences in kF along GY and GX. Using this analysis, a new, linear relationship emerges between the hole-doping derived from ARPES, p(ARPES), and that derived using from the Presland relation, p(Presland), such that p(ARPES) = p(Presland) + 0.11. The implications for this difference between the ARPES- and Presland-derived estimates for p are discussed and possible future directions to elucidate the origin of this discrepancy are presented.

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