Electronic structures and photoemission spectroscopy

Abstract:

MnBi2Te4-based superlattices not only enrich the materials family of magnetic topological insulators, but also offer a platform for tailoring magnetic properties and interlayer magnetic coupling through the strategic insertion layer design. Here, we present the electrical and magnetic characterization of (Bi1-xSbx)2Te3-intercalated MnBi2Te4 multilayers grown by molecular beam epitaxy. By precisely adjusting the Sb-to-Bi ratio in the spacer layer, the magneto-transport response is modulated, unveiling the critical role of Fermi level tuning in optimizing the anomalous Hall signal and reconfiguring the magnetic ground state. Moreover, by varying the interlayer thickness, tunable magnetic coupling is achieved, enabling precise control over ferromagnetic and antiferromagnetic components. These findings pave the way for the exploration of versatile magnetic topological phases in quantum materials systems.

Abstract:

Over the years, great efforts have been devoted in introducing a sizable and tunable band gap in graphene for its potential application in next‐generation electronic devices. The primary challenge in modulating this gap has been the absence of a direct method for observing changes of the band gap in momentum space. In this study, advanced spatial‐ and angle‐resolved photoemission spectroscopy technique is employed to directly visualize the gap formation in bilayer graphene, modulated by both displacement fields and moiré potentials. The application of displacement field via in situ electrostatic gating introduces a sizable and tunable electronic bandgap, proportional to the field strength up to 100 meV. Meanwhile, the moiré potential, induced by aligning the underlying hexagonal boron nitride substrate, extends the bandgap by ≈20 meV. Theoretical calculations effectively capture the experimental observations. This investigation provides a quantitative understanding of how these two mechanisms collaboratively modulate the band gap in bilayer graphene, offering valuable guidance for the design of graphene‐based electronic devices.