Layered Topological Insulators and Semimetals for Magnetoresistance Type Sensors

Abstract

Magnetoresistance (MR) type sensors are transducers that can vary their resistances sensitively in response to an applied magnetic field. Recently, topological quantum materials have drawn the increased attention for sensor applications due to their novel MR effects. Here, a range of MR effects occurring in the layered 3D topological insulators and topological semimetals are briefly reviewed. The MR effects include the extremely large nonsaturating MR, the giant anisotropic MR, and the unique spin‐valve‐like MR. The large MR ratios, the high MR anisotropy, and the low 1/f noise allow sensors to have the high sensitivity over a wide range of temperatures and magnetic fields. It is anticipated that the layered topological quantum materials with their excellent MR performance and structural flexibility would provide an ideal platform for new‐generation magnetic sensor applications.

Tunable Open‐Access Microcavities for Solid‐State Quantum Photonics and Polaritonics

“…Especially, the existence of large TE–TM polarization splitting in the open‐access microcavity renders it a unique system of photonic spin–orbit (SO) coupling. Indeed, for 2D polaritons created in planar microcavities, the TE–TM splitting acts as an effective magnetic field on cavity photons, leading to interesting phenomena such as optical spin Hall effect, magnetic‐monopole‐like half dark solitons, and polaritonic topological insulators . Dufferwiel et al.…”

“…[63][64][65] Moreover, the transverse electric-transverse magnetic (TE-TM) mode splitting and external magnetic field are demonstrated to affect the polaritonic spin via the photonic and excitonic parts respectively, [9,66,67] which eventually led to the demonstration of polaritonic topological insulators. [8,9,68,69]…”

“…Indeed, for 2D polaritons created in planar microcavities, the TE-TM splitting acts as an effective magnetic field on cavity photons, leading to interesting phenomena such as optical spin Hall effect, [67] magnetic-monopole-like half dark solitons, [88] and polaritonic topological insulators. [8,9,69] Dufferwiel et al reported polariton condensates exhibiting vortex-like pseudospin textures in a chip-based open-access microcavity. [89] A combined effect of the confinement potential created by the concave mirror and the spin-orbit coupling induced by the large TE-TM splitting results in a lifting of degeneracy of the first excited manifold (corresponding to LG mode with (p, |l|) = (0, 1)), showing eigenstates of radial/azimuthal spin vortices and hyperbolic-like spin antivortices (Figure 9a).…”

Quantum Technologies are (in) QUTE

“…Now, what do we have in store for the New Year: The present issue features, for example, a Review on topological insulators and semimetals for magnetoresistive sensors and a Progress Report on the Dicke model being relevant for quantum optics . Later during 2019, we also plan to present two special issues on the topics of Quantum Machine Learning and Photonic Quantum Technologies that will aim to provide a snapshot of the state‐of‐the‐art in these respective fields.…”

“…The first three issues published in 2018 already provided a glimpse of our intended broad topical spectrum, with Reviews on continuous-variable quantum key distribution, [3] non-equilibrium Bose-Einstein-like condensation [4] and integrated quantum photonics based on diamond, [5] accompanied by original research contributions as Communications or Full Papers. Now, what do we have in store for the New Year: The present issue features, for example, a Review on topological insulators and semimetals for magnetoresistive sensors [6] and a Progress…”