  Stanene, a single atomic layer of Sn in a honeycomb lattice, is predicted a
candidate wide bandgap two-dimensional (2D) topological insulator and can host
intriguing topological states of matter such as quantum anomalous Hall effect
and topological superconductivity with different surface modifications. Despite
intensive research efforts, one still cannot obtain bulk-insulating stanene
samples-a prerequisite for any transport studies and applications of stanene.
Here we show the experimental realization of an epitaxial stanene with an
insulating bulk bandgap by using PbTe(111) substrates. With low-temperature
molecular beam epitaxy, we are able to grow single layer stanene on PbTe(111).
In-situ angle-resolved photoemission spectroscopy shows the characteristic
stanene bands with its Fermi level lying in the bandgap. Doping Sr in PbTe
removes the substrate states located in the stanene gap, resulting in a stanene
sample with truly insulating bulk. This experimental progress paves the way for
studies of stanene-based topological quantum effects.
