  Combining magnetism and nontrivial band topology gives rise to quantum
anomalous Hall (QAH) insulators and exotic quantum phases such as the QAH
effect where current flows without dissipation along quantized edge states.
Inducing magnetic order in topological insulators via proximity to a magnetic
material offers a promising pathway towards achieving QAH effect at high
temperature for lossless transport applications. One promising architecture
involves a sandwich structure comprising two single layers of MnBi2Te4 (a 2D
ferromagnetic insulator) with ultra-thin Bi2Te3 in the middle, and is predicted
to yield a robust QAH insulator phase with a bandgap well above thermal energy
at room temperature (25 meV). Here we demonstrate the growth of a 1SL MnBi2Te4
/ 4QL Bi2Te3 /1SL MnBi2Te4 heterostructure via molecular beam epitaxy, and
probe the electronic structure using angle resolved photoelectron spectroscopy.
We observe strong hexagonally warped massive Dirac Fermions and a bandgap of 75
meV. The magnetic origin of the gap is confirmed by the observation of broken
time reversal symmetry and the exchange-Rashba effect, in excellent agreement
with density functional theory calculations. These findings provide insights
into magnetic proximity effects in topological insulators, that will move
lossless transport in topological insulators towards higher temperature.
