Spin-transfer torque generated in graphene based topological insulator heterostructures

Artificial Neuronal Devices Based on Emerging Materials: Neuronal Dynamics and Applications

Artificial neuronal devices are critical building blocks of neuromorphic computing systems and currently the subject of intense research motivated by application needs from new computing technology and more realistic brain emulation. Researchers have proposed a range of device concepts that can mimic neuronal dynamics and functions. Although the switching physics and device structures of these artificial neurons are largely different, their behaviors can be described by several neuron models in a more unified manner. In this paper, the reports of artificial neuronal devices based on emerging volatile switching materials are reviewed from the perspective of the demonstrated neuron models, with a focus on the neuronal functions implemented in these devices and the exploitation of these functions for computational and sensing applications. Furthermore, the neuroscience inspirations and engineering methods to enrich the neuronal dynamics that remain to be implemented in artificial neuronal devices and networks toward realizing the full functionalities of biological neurons are discussed.

Resonant Photovoltaic Effect in Doped Magnetic Semiconductors

The rectified nonlinear response of a clean, time-reversal symmetric, undoped semiconductor to an ac electric field includes a well known intrinsic shift current. We show that when Kramers degeneracy is broken, a distinct second order rectified response appears due to Bloch state anomalous velocities in a system with an oscillating Fermi surface. This effect, which we refer to as the resonant photovoltaic effect, produces a resonant galvanic current peak at the interband absorption threshold in doped semiconductors or semimetals with approximate particle-hole symmetry. We evaluate the resonant photovoltaic effect for a model of the surface states of a magnetized topological insulator.

Helical edge states of topological photonic crystals with line defects

Topologically protected edge states of honeycomb photonic crystals (PCs) have been extensively studied in recent years. Here we propose several optimized two-dimensional PC configurations with distinct line defects introduced by breaking the C₆ symmetry of each topological lattice along the interfaces between two different topologies. The spin-flipping nature of the defect modes of these PC configurations is measured, which is expected to offer a novel realization mechanism of quantum spin Hall effect. The line defects can be treated as unidirectional air waveguides due to the characteristic topological properties. We manipulate the coupling effect of two helical edge states with tunable waveguide widths. It shows that the air waveguide has possibility for practical applications because of its suppression of backward scattering and considerable transmission efficiency.