Noncollinear exchange interaction in transition metal dichalcogenide edges

We study the Ruderman-Kittel-Kasuya-Yosida effective exchange interaction between magnetic impurities embedded on the edges of transition-metal dichalcogenide flakes, using a three-orbital tight-binding model. Electronic states lying midgap of the bulk structure have strong one-dimensional (1D) character, localized on the edges of the crystallite. This results in exchange interactions with $1/r$ (or slower) decay with distance $r$, similar to other 1D systems. Most interestingly, however, the strong spin-orbit interaction in these materials results in sizable non-collinear Dzyaloshinskii-Moriya interactions between impurities, comparable in size to the usual Ising and in-plane components. Varying the relevant Fermi energy by doping or gating may allow one to modulate the effective interactions, controlling the possible helical ground state configurations of multiple impurities.Comment: 5 pages and 4 figure

Lateral Interfaces of Transition Metal Dichalcogenides: A Stable Tunable One-Dimensional Physics Platform

We study in-plane lateral heterostructures of commensurate transition-metal dichalcogenides, such as MoS$_{2}$-WS$_{2}$ and MoSe$_{2}$-WSe$_{2}$, and find interfacial and edge states that are highly localized to these regions of the heterostructure. These are one-dimensional (1D) in nature, lying within the bandgap of the bulk structure and exhibiting complex orbital and spin structure. We describe such heteroribbons with a three-orbital tight-binding model that uses first principles and experimental parameters as input, allowing us to model realistic systems. Analytical modeling for the 1D interfacial bands results in long-range hoppings due to the hybridization along the interface, with strong spin-orbit couplings. We further explore the Ruderman-Kittel-Kasuya-Yosida indirect interaction between magnetic impurities located at the interface. The unusual features of the interface states result in effective long-range exchange non-collinear interactions between impurities. These results suggest that transition-metal dichalcogenide interfaces could serve as stable, tunable 1D platform with unique properties for possible use in exploring Majorana fermions, plasma excitations and spintronics applications.Comment: 12 pages, 7 figure

Temporal plasmonics: Fano and Rabi regimes in the time domain in metal nanostructures

The Fano and Rabi models represent remarkably common effects in optics. Here we study the coherent time dynamics of plasmonic systems exhibiting Fano and Rabi resonances. We demonstrate that these systems show fundamentally different dynamics. A system with a Fano resonance displays at most one temporal beat under pulsed excitation, whereas a system in the Rabi regime may have any number of beats. Remarkably, the Fano-like systems show time dynamics with very characteristic coherent tails despite the strong decoherence that is intrinsic for such systems. The coherent Fano and Rabi dynamics that we predicted can be observed in plasmonic nanocrystal dimers in time-resolved experiments. Our study demonstrates that such coherent temporal plasmonics includes nontrivial and characteristic relaxation behaviors and presents an interesting direction to develop with further research.Comment: 31 pages [main text (4 figures) + supplemental (12 figures)

Symmetries and hybridization in the indirect interaction between magnetic moments in MoS2 nanoflakes

We study the Ruderman-Kittel-Kasuya-Yosida interaction between magnetic impurities embedded in p-doped transition metal dichalcogenide triangular flakes. The role of underlying symmetries is exposed by analyzing the interaction as a function of impurity separation along zigzag and armchair trajectories, in specific parts of the sample. The large spin-orbit coupling in these materials produces strongly anisotropic interactions, including a Dzyaloshinskii-Moriya component that can be sizable and tunable. We consider impurities hybridized to different orbitals of the host transition metal and identify specific characteristics for onsite and hollow site adsorption. In the onsite case, the different components of the interaction have similar magnitude, while for the hollow site, the Ising component dominates. We also study the dependence of the interaction with the level of hole doping, which supplies a further degree of tunability. Our results could provide ways of controlling helical long range spin order in magnetic impurity arrays embedded in these materials.Fil: Ávalos-Ovando, Oscar. Ohio University; Estados UnidosFil: Mastrogiuseppe, Diego Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Ulloa, Sergio E.. Ohio University; Estados Unido

Temporal plasmonics: Fano and Rabi regimes in the time domain in metal nanostructures

The Fano and Rabi models represent remarkably common effects in optics. Here we study the coherent time dynamics of plasmonic systems exhibiting Fano and Rabi spectral responses. We demonstrate that these systems show fundamentally different dynamics. A plasmonic system with a Fano resonance displays at most one temporal beat under pulsed excitation, whereas a plasmonic system in the Rabi-like regime may have any number of beats. Remarkably, the Fano-like systems show time dynamics with very characteristic coherent tails despite the strong decoherence that is intrinsic for such systems. The coherent Fano and Rabi dynamics that we predicted can be observed in plasmonic nanocrystal dimers in time-resolved experiments. Our study demonstrates that such coherent temporal plasmonics includes non-trivial and characteristic relaxation behaviors and presents an interesting direction to develop with further research

Local growth mediated by plasmonic hot carriers: chirality from achiral nanocrystals using circularly polarized light

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGPlasmonic nanocrystals and their assemblies are excellent tools to create functional systems, including systems with strong chiral optical responses. Here we study the possibility of growing chiral plasmonic nanocrystals from strictly nonchiral seeds of different types by using circularly polarized light as the chirality-inducing mechanism. We present a novel theoretical methodology that simulates realistic nonlinear and inhomogeneous photogrowth processes in plasmonic nanocrystals, mediated by the excitation of hot carriers that can drive surface chemistry. We show the strongly anisotropic and chiral growth of oriented nanocrystals with lowered symmetry, with the striking feature that such chiral growth can appear even for nanocrystals with subwavelength sizes. Furthermore, we show that the chiral growth of nanocrystals in solution is fundamentally challenging. This work explores new ways of growing monolithic chiral plasmonic nanostructures and can be useful for the development of plasmonic photocatalysis and fabrication technologies.Xunta de Galicia | Ref. ED431C 2016-034Xunta de Galicia | IN607A 2018/5Agencia Estatal de Investigación | Ref. CTM2017-84050-RAgencia Estatal de Investigación | Ref. PID2020-113704RB-I00Agencia Estatal de Investigación | Ref. PID2020-118282RA-I0

Visible Light-Induced Reactivity of Plasmonic Gold Nanoparticles Incorporated into TiO2 Matrix towards 2-Chloroethyl Ethyl Sulfide

Inexpensive strategies for efficient decontamination of hazardous chemicals are required. In this study, the effect of visible light (λ > 400 nm) on the decomposition of 2-chloroethyl ethyl sulfide (2-CEES, a sulfur mustard (HD) simulant) on Au/TiO2 photocatalyst under anaerobic and aerobic conditions has been investigated in situ by diffuse reflectance infrared Fourier –transformed spectroscopy (DRIFTS). Under anaerobic conditions, 2-CEES partially desorbs from the Au/TiO2 surface likely due to the photothermal effect, induced by photo-excited plasmonic Au nanoparticles. In the aerobic experiment, no visible light effect is observed. We attribute this behavior to 2-CEES consumption by hydrolysis to 2-ethylthio ethanol in the dark, prior to visible light excitation. Oxygen activates water molecules in the dark, resulting in accelerated 2-CEES hydrolysis