Fermi surface of superconducting cuprates

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Fig. 1. The Fermi surface of bi-layer BSCCO, calculated (left) and measured by ARPES (right). The dashed rectangle represents the first Brillouin zone.

The electronic structure of superconducting cuprates, also called high temperature superconductors (HTSC), is highly anisotropic. First, the cuprates are almost two-dimensional (2D): the conducting electrons are mainly localized in the CuO2 layers, the common building blocks of all HTSC compounds (e.g., see the crystal structure of YBCO or BSCCO). Therefore, the Fermi surface of HTSC is very close to the Fermi surface of the doped CuO2 plane (or multi-planes, in case of multi-layer cuprates) and can be presented on the 2D reciprocal space (or momentum space) of the CuO2 lattice. The typical Fermi surface within the first CuO2 Brillouin zone is sketched in Fig. 1 (left). It can be derived from the band structure calculations or measured by angle resolved photoemission spectroscopy (ARPES). Fig. 1 (right) shows the Fermi surface of BSCCO measured by ARPES. In a wide range of charge carrier concentration (doping level), in which the hole-doped HTSC are superconducting, the Fermi surface is hole-like (i.e. open, as shown in Fig. 1). This results in an inherent in-plane anisotropy of the electronic properties of HTSC.