Structural Origin of Apparent Fermi Surface Pockets in Angle-Resolved Photoemission of ${\mathrm{Bi}}_2{\mathrm{Sr}}_{2-x}{\mathrm{La}}_x{\mathrm{CuO}}_{6+\delta }$

We observe apparent hole pockets in the Fermi surfaces of single-layer Bi-based cuprate superconductors from angle-resolved photoemission. From detailed low-energy electron diffraction measurements and an analysis of the angle-resolved photoemission polarization dependence, we show that these pockets are not intrinsic but arise from multiple overlapping superstructure replicas of the main and shadow bands. We further demonstrate that the hole pockets reported recently from angle-resolved photoemission [Meng et al., Nature (London) 462, 335 (2009)] have a similar structural origin and are inconsistent with an intrinsic hole pocket associated with the electronic structure of a doped ${\mathrm{CuO}}_2$ plane.

Figure 1

ARPES Fermi surface of (a) UD14.5K and (b) OP30K La-Bi2201, measured with $p$ polarization. Extracted contours (blue circles) and a tight-binding model of the main (solid line), shadow (dashed line), and $\pm {\mathbf{q}}_1$ or $\pm 2{\mathbf{q}}_1$ (green), $\pm {\mathbf{q}}_2$ (blue), and $\pm ({\mathbf{q}}_1+{\mathbf{q}}_2)$ (red) umklapp bands are overlaid on the data. LEED from (c) UD14.5K and (d) OP30K La-Bi2201. A magnified view of the blue region and a line cut along the $\Gamma \mathrm{\text{−}}Y$ direction (red line) are shown to the left of and below each pattern, respectively. Extracted peak positions (red dots) and those expected for superstructure peaks at ${\mathbf{k}}_0\pm m_1{\mathbf{q}}_1\pm m_2{\mathbf{q}}_2$ (vertical gray lines) are in good agreement. The inset in (a) shows a simplified Fermi surface with only the main (MB) and shadow (SB) bands.

Figure 2

(a) LEED pattern and (b) ARPES Fermi surface of OP35K (Pb,La)-Bi2201, showing the presence of two superstructure vectors, and the resulting apparent pockets in the Fermi surface. A tight-binding model, using superstructure vectors determined from the LEED analysis, is also shown in (b).

Figure 3

Polarization dependence of ARPES. (a) Dispersion along $\Gamma \mathrm{\text{−}}Y$ of OP30K La-Bi2201. (b),(c) Dispersion close to the equivalent direction in the 2nd Brillouin zone [along dashed lines in (d)] of OP30K and UD14.5K La-Bi2201. (d) ARPES Fermi surface of UD14.5K La-Bi2201. All spectra were measured with $p$ (top) and $s$ (bottom) polarization.

Figure 4

(a) LEED of UD20K La-Bi2201. (b) Red circles reproduce the Fermi-surface contours of UD18K La-Bi2201 from Ref. 7. A tight-binding Fermi surface including umklapp bands derived from our LEED analysis reproduces all features of the data from Meng et al. [7] including the apparent Fermi-surface pockets (labeled LP, HP, and LPS after Ref. 7). The tight-binding bands are labeled by $(m_1,m_2{)}^{{[}^{\prime }]}$, where $m_i$ is the order of the $({\mathbf{q}}_1,{\mathbf{q}}_2)$ superstructure replica and a prime denotes the shadow band.