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The percolation plays an essential role in the physics of plateau transition, localization, and breakdown in quantum Hall (QH) systems. In practice, it always exists probably due to sample imperfections and has to be addressed before realizing the full potentials of topological electronics and qubits. Here, we investigate the cause, distribution, and number of the percolation in a quantum anomalous Hall (QAH) insulator of an anti-Hall bar geometry with two perimeters, which allows for probing both the inter- and intra-perimeter percolations by injecting currents into either or both perimeters. We discover the dual-QAH effect with opposite chiralities from these two perimeters, which exhibits linear modulations by the currents applied to both perimeters. By solving the formulation of such modulations with the Landauer–Büttiker formalism, the distribution and number of the inter-perimeter percolative channels could be identified. Strikingly, a dissipative constituent is detected in the transport of the QAH state, as revealed by the linear scalings in longitudinal conductivities versus the sum of currents injected to both perimeters, similar to that in the trivial-insulating state. Such a behavior unveils the quasi-2D nature of the intra-perimeter percolation, which superimposes onto and perturbs the dissipationless chiral edge transport. The formation of percolations is ascribed to the joint effect of the electric field, finite conductivity, and sample imperfections.

The Chern insulator manifests itself via the surface quantized Hall current and magnetoelectric effect. The manipulation of surface magnetizations enables a control of the dissipationless chiral transport and thus allows for potential applications of topological magnetoelectric devices with low-energy consumption. Here, we present experimental studies of bias-modulated switching the magnetic states utilizing the magnetoelectric coupling in a Chern insulator. This is achieved via applying a d.c. bias across the source and drain at various magnetic states, during which an effective magnetic field is developed to switch the quantum anomalous Hall state towards its opposite. Comprehensive transport studies show that the switch efficiency is proportional to the amplitude and applying time of the bias, depends on the initial magnetic state, but is insensitive to the electric polarity. Our results provide an efficient scheme to manipulate the Chern insulator and understanding on the electric breakdown of chiral edge states.

We have developed an incandescent Mo source to fabricate large-area single-crystalline MoSe2 thin films. The as-grown MoSe2 thin films were characterized using transmission electron microscopy, energy dispersive x-ray spectroscopy, atomic force microscopy, Raman spectroscopy, photoluminescence (PL), reflection high energy electron diffraction (RHEED) and angular resolved photoemission spectroscopy (ARPES). A new Raman characteristic peak at 1591 cm−1 was identified. Results from Raman spectroscopy, PL, RHEED and ARPES studies consistently reveal that large-area single crystalline mono-layer of MoSe2 could be achieved by this technique. This technique enjoys several advantages over conventional approaches and could be extended to the growth of other two-dimensional layered materials containing a low-vapor-pressure element. [ABSTRACT FROM AUTHOR]