Shubnikov de Haas (SdH) oscillations and Angle Resolved PhotoEmission Spectroscopy (ARPES) are used to probe the Fermi surface of single crystals of Bi2Se3. We find that SdH and ARPES probes quantitatively agree on measurements of the effective mass and bulk band dispersion. In high carrier density samples, the two probes also agree in the exact position of the Fermi level EF , but for lower carrier density samples discrepancies emerge in the position of EF . In particular, SdH reveals a bulk three-dimensional Fermi surface for samples with carrier densities as low as 10 17 cm −3 . We suggest a simple mechanism to explain these differences and discuss consequences for existing and future transport studies of topological insulators.

a b s t r a c tHigh quality single crystals of Cs 2 Au 2 X 6 (X ¼ Br,I) were grown using a ternary self-flux method. Structural refinements based on single crystal X-ray diffraction measurements show that both materials have a distorted perovskite structure belonging to the I4/mmm space group with full site occupancy. Transport measurements reveal a large bandgap of 550 7 100 meV for Cs 2 Au 2 I 6 and 520 7 80 meV for Cs 2 Au 2 Br 6 . Initial attempts at chemical substitution are described.Published by Elsevier B.V.