In contrast, the optical activity in the bulk WSM is dominated by axion electrodynamics, which persists even in the Pauli-blocked regime of no optical transitions. In bulk WSMs, Q acts analogously to the magnetization in magnetic materials, leading to a large polar Kerr effect linear in Q , when light is incident on the WSM surface without Fermi arc states, and the Voigt effect quadratic in Q , when light is incident on surface with Fermi arc states.
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To address this, we have been improving access via several different mechanisms. The vertical blue lines mark the boundary values for transition frequencies for regions I and II, i. All other parameters are identical to those of Fig. In this Faraday geometry, light propagates along the direction of the Weyl node separation, with large circular birefringence and dichroism.
The solid horizontal line in both c and d shows the vanishing small optical activity if the axion term is neglected. Thus the optical activity is caused predominantly by the axion term. Interestingly, it should be observable also in the Pauli-blocked region where no optical transitions are allowed.
Here, all the parameters are identical to those of Fig. In this Voigt geometry, light propagates perpendicular to the Weyl node separation, with large linear birefringence and dichroism. The solid lines in both c and d show the corresponding optical activity if the axion term is neglected. Learn about our response to COVID , including freely available research and expanded remote access support.
B , — Published 28 August Research Areas. Kerr effect Optical conductivity Topological phases of matter. Physical Systems. The optical constants of the fabricated activity. Besides, metallic nanoparticles present structures were obtained from spectral ellipsometry surface plasmon resonances which enhance their mag- measurements at different incident angles 45—75 neto-optical activity Melle et al. For TEM measurements, the thin films in which Co nanoparticles have been nanoparticles were deposited on a carbon-coated incorporated into a SiOx matrix by sequential depo- cooper TEM grid.
The nanoparticles have been generated using an Ion Cluster Source ICS , allow- ing a precise control on the nanoparticle diameter as Results and discussion well as their concentration in the dielectric matrix. The deposition of SiOx was performed by radio Growth and morphology frequency RF magnetron sputtering. By controlling the amount of Co nanoparticles in the SiOx matrix, The structures were obtained by alternate deposition with a Co concentration in volume between 0. The activity in a wide spectral range have been prepared.
The Co volume concentration is presented and discussed. The density of nanoparticles was Experimental details calculated from the number of clusters by layer obtained with AFM on reference samples grown Sample deposition was carried out in an ultra- before each sample. Samples with 0. The deposition of SiOx was done influence of Co concentration on both the optical and by RF magnetron sputtering from a SiO2 target— the magneto-optical properties. Co cluster deposition profile. As can be observed, the distribution of the was carried out using an Oxford Applied Research nanoparticles is relatively homogeneous.
The statis- Oxford A. Inset diameter distribution profile of more than Co clusters. This can be clearly appreciated in Fig. However, while AFM is not suited for the determination of the in-plane dimensions, it is well-suited for the determination of the out-of-plane dimensions where the convolution of the AFM tip with the measured structures is negligible.
Therefore, the authors have used the AFM to determine the height of the particles. An example is displayed in Fig. The statistical analysis of the AFM images gives an average height of Worthy of mention, the apparent physical contact between particles observed in the AFM images is, in most of cases, due to the mentioned tip convolution, being actually isolated as observed by TEM. Optical and magneto-optical properties In Fig.
Taking into account that the Co clusters have approximately the same diameter as the SiOx layer, the authors can consider all structure as an effective medium. As can be observed in Fig. Such spectral behavior is the one expected for a system made of a dielectric matrix with a very low concen- tration of metallic nanoparticles. Assuming for the nanoparticles a simple core—shell structure, the authors have simulated the optical properties of the system using the formalism devel- oped by Abe and Suwa The thin continuous lines in Fig.
As can be observed, this core—shell structure reproduces the values and wavelength dependence of the experimental results and supports the core—shell structure suggested by the magnetic measurements. In Fig. As expected, a gradual increase in the magneto-optical activity is observed as a function of Co concentration. Worthy Fig. These large values of rotation and structure for the nanoparticles instead of pure Co ellipticity are purely optical effects and are due to the extremely low reflectivity values of these structures and Levy and Stroud The thick continuous line in these wavelengths, as can be seen in Fig.
Therefore, a strong and on a nm-thick layer of SiOx grown in the same reduction of the reflectivity rpp will necessarily conditions as the SiOx of the Co nanoparticle layers. As can be observed, although the simulated and Finally, in Fig. They values are much higher than the experimental ones. As expected, the absolute particles Clavero et al.
As a matter of ous lines in Fig.
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