Masataka Mogi

Quantum anomalous Hall effect (QAHE), which generates dissipation-less edge current without external magnetic field, is observed in magnetic-ion doped topological insulators (TIs) such as Cr- and V-doped (Bi,Sb)2Te3. The QAHE emerges when the Fermi level is inside the magnetically induced gap around the original Dirac point of the TI surface state. Although the size of gap is reported to be about 50 meV, the observable temperature of QAHE has been limited below 300 mK. We attempt magnetic-Cr mod

We report a proximity-driven large anomalous Hall effect in all-telluride heterostructures consisting of the ferromagnetic insulator Cr_{2}Ge_{2}Te_{6} and topological insulator (Bi,Sb)_{2}Te_{3}. Despite small magnetization in the (Bi,Sb)_{2}Te_{3} layer, the anomalous Hall conductivity reaches a large value of 0.2e^{2}/h in accord with a ferromagnetic response of the Cr_{2}Ge_{2}Te_{6}. The results show that the exchange coupling between the surface state of the topological insulator and the p

Electrical manipulation of magnetization could be an essential function for energy-efficient spintronics technology. A magnetic topological insulator, possessing a magnetically gapped surface state with spin-polarized electrons, not only exhibits exotic topological phases relevant to the quantum anomalous Hall state but also enables the electrical control of its magnetic state at the surface. Here, we demonstrate efficient current-induced switching of the surface ferromagnetism in hetero-bilayer

Ferromagnetic van der Waals (vdW) insulators possess robust magnetic order even in a few layers of two-dimensional sheets. The heterostructures of such vdW materials prepared by molecular-beam epitaxy (MBE) are one of the ideal platforms for exploration of novel electronic/spintronic functionalities based on their ferromagnetism via an abrupt hetero-interface. Here we report successful MBE-growth of a vdW magnetic insulator Cr2Ge2Te6 thin film on a topological insulator (Bi,Sb)2Te3. Metal to ins

Ultrafast photoexcitation offers a novel approach to manipulating quantum materials. One of the long-standing goals in this field is to achieve optical control over topological properties. However, the impact on their electronic structures, which host gapless surface states, has yet to be directly observed. Here, using time- and angle-resolved photoemission spectroscopy, we visualize the photoinduced evolution of the band structure in Bi_{y}(Pb_{1-x}Sn_{x})_{1-y}Se(111) films from topological to

Topological phases are a new class of quantum phases of materials, of which the transition is characterized by the change of the topological invariants. If the topological invariant can be controlled by external stimuli, we can manipulate the emergent properties such as the edge and surface states. The magnetic topological insulator based heterostructures are a great arena to realize that by utilizing top and bottom surface degrees of freedom. In this chapter, we present the evidence of phase tr

Ultrafast optical excitation provides a powerful route for accessing emergent quantum phases far from equilibrium, enabling transient light-induced phenomena such as magnetism, ferroelectricity, and superconductivity. However, extending this approach to induce topological phases, especially in conventional semiconductors, remains challenging. Here, we report the observation of a thermally inaccessible, transient topological crystalline order in the layered semiconductor SnSe, a trivial insulator