  A long-standing issue in topological insulator research has been to find a
material that provides an ideal platform for characterizing topological surface
states without interference from bulk electronic states and can reliably be
fabricated as bulk crystals. This material would be a bulk insulator, have a
surface state Dirac point energy well isolated from the bulk valence and
conduction bands, have high surface state electronic mobility, and be growable
as large, high quality bulk single crystals. Here we show that this major
materials obstacle in the field is overcome by crystals of lightly Sn-doped
Bi1.1Sb0.9Te2S (Sn-BSTS) grown by the Vertical Bridgeman method, which we
characterize here via angle-resolved photoemission spectroscopy, scanning
tunneling microscopy, transport studies of the bulk and surface states, and
X-ray diffraction and Raman scattering. We present this new material as a bulk
topological insulator that can be reliably grown and studied in many
laboratories around the world.
