Manipulating Weyl quasiparticles by orbital-selective photoexcitation in WTe2

Abstract

Optical control of structural and electronic properties of Weyl semimetals allows development of switchable and dissipationless topological devices at the ultrafast scale. An unexpected orbital-selective photoexcitation in type-II Weyl material WTe2 is reported under linearly polarized light (LPL), inducing striking transitions among several topologically-distinct phases mediated by effective electron-phonon couplings. The symmetry features of atomic orbitals comprising the Weyl bands result in asymmetric electronic transitions near the Weyl points, and in turn a switchable interlayer shear motion with respect to linear light polarization, when a near-infrared laser pulse is applied. Consequently, not only annihilation of Weyl quasiparticle pairs, but also increasing separation of Weyl points can be achieved, complementing existing experimental observations. In this work, we provide a new perspective on manipulating the Weyl node singularity and coherent control of electron and lattice quantum dynamics simultaneously.

Ultrafast Ferroelectric Ordering on the Surface of a Topological Semimetal MoTe2

“…Moreover, such ferroelectric ordering is a direct consequence of a novel form of dielectric screening, with its geometry resembling ferroelectric large polaron screening , proposed to account for the remarkable charge carrier screening and optoelectronic properties of lead halide perovskites. Finally, because the electronic band structure topology of MoTe 2 at the Fermi level is sensitive to the material inversion symmetry, the effective surface electric field of IPS electrons, which can transiently modify the local lattice and electronic polarizations, may serve to control the nontrivial electronic band topology, such as Lifshitz transition, Weyl point separation, , and magnetoelectric gyrotropic response, as well as inducing magnetic monopoles and fractional anion excitations for quantum computations via coupling to axial current between Weyl nodes on ultrafast time scales.…”

Giant bulk photovoltaic effect driven by the wall-to-wall charge shift in WS2 nanotubes

“…To examine the effect of atomic motions, accompanied by the carrier excitation on the shift-current generation mechanism, we repeat the same real-time photocurrent calculations through the Ehrenfest dynamics, in which atomic motions are progressed through the instantaneous forces 59 . We tested with the light frequencies corresponding to the peaks in the shift current spectra (the inset of Fig.…”

Machine Learning Driven Synthesis of Few-Layered WTe2 with Geometrical Control

“…In the past few decades, two-dimensional (2D) transition metal chalcogenides (TMCs) have demonstrated excellent performance in nanoelectronic and spintronic applications and showed great potential for investigating quantum physics and fabricating quantum devices. − Recently, one-dimensional (1D) nanostructures derived from 2D TMCs have received increasing attention, attributed to the intriguing properties that arise from the reduced dimensionality and enhanced quantum confinement effect. − Among TMCs, tungsten ditelluride (WTe 2 ) with rich structural variations and strong spin–orbit coupling is predicted to be type-II Weyl semimetals and 2D topological insulators, providing an ideal platform for the investigation of dimensionality-related properties, such as superconductivity, quantum spin Hall Effect, and Majorana Fermion. ,,− Even though chemical vapor deposition (CVD) has been widely adopted to grow high-quality 2D materials, controllable synthesis of few-layered WTe 2 remains challenging, not to mention the dimensionality control. This is due to the lower reactivity of Te and small electronegativity difference between Te and W, as well as the poor stability of telluride. − Effective identification of optimal synthesis conditions for WTe 2 with dimensional tunability is therefore urgently required.…”