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The accuracy of Hall resistance in the quantum anomalous Hall effect has been studied at zero magnetic field using Crx(Bi,Sb) 2 − x Te3-based magnetic heterostructure films of topological insulators. The measured deviation of the Hall resistance from its theoretical value h / e 2 was less than 2 ppm when the source drain current was 30 nA. This result has verified that the quantization of the Hall resistance is very accurate in the magnetic heterostructure films and in the previously reported uniformly doped films.

The quantum anomalous Hall effect (QAHE) is an exotic quantum phenomenon originating from dissipation-less chiral channels at the sample edge. While the QAHE has been observed in magnetically doped topological insulators (TIs), exploiting magnetic proximity effect on the TI surface from adjacent ferromagnet layers may provide an alternative approach to the QAHE by opening an exchange gap with less disorder than that in the doped system. Nevertheless, the engineering of a favorable heterointerface that realizes the QAHE based on the magnetic proximity effect remains to be achieved. Here, we report on the observation of the QAHE in a proximity coupled system of non-magnetic TI and ferromagnetic insulator (FMI). We have designed sandwich heterostructures of (Zn,Cr)Te/(Bi,Sb)2Te3/(Zn,Cr)Te that fulfills two prerequisites for the emergence of the QAHE; the formation of a sizable exchange gap at the TI surface state and the tuning of the Fermi energy into the exchange gap. The efficient proximity coupling in the all-telluride based heterostructure as demonstrated here will enable a realistic design of versatile tailor-made topological materials coupled with ferromagnetism, ferroelectricity, superconductivity, and so on., 18 pages, 4 figures

We report on emergence of two-dimensional conduction and ferromagnetism at the interface of MnTe thin films and InP substrates. The MnTe/InP heterostructures grown by molecular-beam epitaxy show thickness-independent sheet conductivity above a critical thickness of about 20 nm, indicating the formation of a conducting layer at the interface. Furthermore, the ferromagnetic behavior is confirmed by both magnetization and anomalous Hall effect measurements below a critical temperature of 270 K. The critical temperature is also independent of the thickness. By the investigation of the atomic structure with transmission electron microscopy, we observe a structural anomaly near the interface which consists of an antiprism-type Mn network unlike a prism-type Mn network of conventional MnTe. The band structure calculation shows that the antiprism-type MnTe can host metallic conduction and ferromagnetism, which is consistent with the present experimental results. The interface engineering based on the chalcogenide compound will develop a new arena for designing the emergent low dimensional conduction and magnetism.

Electric field penetration into the metallic side of a Schottky junction is in principle a universal phenomenon, the magnitude of which increases with the semiconductor permittivity. Here, we quantitatively probe this effect using bias-dependent internal photoemission spectroscopy at the Schottky junction between a large dielectric permittivity semiconductor SrTiO3 and gold. A clear linear reduction in the barrier height with increasing interface electric field was observed, highlighting the importance of field penetration into the gold. The interfacial permittivity of SrTiO3 at the interface is reduced from the bulk value, reflecting intrinsic suppression at the interface.