Magnetic proximity-induced energy gap of topological surface states

Abstract Topological crystalline insulator surface states can acquire an energy gap when time reversal symmetry is broken by interfacing with a magnetic insulator. Such hybrid topological-magnetic insulator structures can be used to generate novel anomalous Hall effects and to control the magnetic state of the insulator in a spintronic device. In this work, we successfully observe the energy gap of topological surface states in proximity with a magnetic insulator using magnetooptical Landau level spectroscopy. The measurements are carried out on Pb1-xSnxSe – EuSe heterostructures grown by molecular beam epitaxy exhibiting record mobility and a low Fermi energy. Through temperature dependent measurements combined with theoretical calculations, we show that the origin of this gap is likely related to quantum confinement, which allows us to conclude that the magnetic proximity effect is weak in this system. The recovered energy gap sets an upper limit for the Fermi level needed to observe the quantized anomalous Hall effect using magnetic proximity heterostructure