Ultrafast modulation of valley dynamics in multiple WS2 − Ag gratings strong coupling system

Abstract

Strong light-matter interactions in two-dimensional transition metal dichalcogenides (TMDCs) with robust spin-valley degrees of freedom open up the prospect of valleytronic devices. A thorough understanding on the dynamics of the valley polarizations in the strong coupling regime is urgently required. Here, multiple polarized TMDCs-SPPs hybrid systems were constructed by combining monolayer WS2 flakes to linear, circular, and spiral Ag gratings, resulting in linear and circular polarized modulation on the coherent hybrid states, respectively. Particularly, valley polaritons can be tailored asymmetrically by chiral strong coupling regime. Furthermore, the dynamics of the polarized polaritons were directly analyzed by transient absorption (TA) measurement. Both of the linear and circular polarization difference in the TA spectra can be retained for a remarkable long time, leading to a polarized PL even at room temperature. More importantly, in the chiral strong coupled WS2-spiral Ag grating devices, the mechanism of the asymmetrical valley-polarized PL (p σ+ = 14.9% and p σ- = 10.8%) is proved by the opposite valley polarization dynamics in the circularly polarized TA spectra. The multiple polarization modulation in monolayer TMDCs-SPPs strong coupling devices could provide a viable route toward multiple polarization polaritonic devices.

Highly aligned organic microwire crystal arrays for high-performance polarization-sensitive photodetectors and image sensors

“…For example, Fang's group [22] achieved a novel self-powered photodetector based on a p-CuZnS/n-TiO 2 nanotube array heterojunction using two-step anodic oxidation. However, unlike inorganic semiconductors, van der Waals forces cause difficulty in achieving large-area single crystals of organic molecules [23][24][25][26]. In addition, most organic materials are susceptible to decomposition when exposed to organic solvents, high temperatures, or strong ultraviolet light, which are commonly used in inorganic semiconductor patterning methods [27][28][29].…”

Light-Shaping of Valley States

“…The steplike structures with pulse duration for the large-amplitude case result from quantum interference between excitations from different pulse cycles (see the Supporting Information). These pure valley currents can be contrasted with previous theoretical work toward valley control in graphene that have relied either on charge scattering off deformation-induced valley contrasting gauge fields, − achieving 60–80% polarization along specific high-symmetry directions, or creating charge contrast via light pulses − with, however, only up to 60–75% valley charge polarization and, moreover, at the price of widespread excitation throughout the Brillouin zone (thus precluding access to valley pure Dirac–Weyl currents).…”

THz induced giant spin and valley currents

“…A long-standing goal in the field of graphene and few-layer graphenes has been to generate a pure valley current. The majority of proposed schemes comprise the design of valley filters, either by using the valley-contrasting gauge field induced by lattice deformation (32)(33)(34)(35) or valley-polarized edge states (36); most recently, valleypolarized scattering states from a biased quantum dot in bilayer graphene have been considered (37). Here, we show that a hencomb pulse applied to biased bilayer graphene results in a fully controllable and 75 to 85% pure valley-polarized current depending on the value of the gap and the dephasing time.…”