Periodic array of quantum rings strongly coupled to circularly polarized light as a topological insulator

We demonstrate theoretically that a strong high-frequency circularly polarized electromagnetic field can turn a two-dimensional periodic array of interconnected quantum rings into a topological insulator. The elaborated approach is applicable to calculate and analyze the electron energy spectrum of the array, the energy spectrum of the edge states and the corresponding electronic densities. As a result, the present theory paves the way to optical control of the topological phases in ring-based mesoscopic structures.Comment: Published versio

Unsettled facts: on the transformational dynamism of evidence in legal discourse

In this article I conduct an examination of discursive identity of a legal ‘object’ in the course of its treatment by various figures in the legal process. The need for this examination arises from a widespread concern about the effects of creating ‘records’, i.e., transforming spoken discourse by way of documentation into ‘evidence’. After a brief review of the current discussion about this phenomenon, I argue that the identity of textualized evidence is upheld by way of references to other texts, all of which create a field of signification within which an object under discussion (evidence) shows different facets without however losing its identity. In order to support my argument, I offer an analysis of ethnographic data pertaining to a specific criminal case. My objective for the analysis is to trace the status of a specific discursive identity after its enunciation during an attorney–client conference. My findings indicate that textualization should be understood not as a form of fixity for discourse, but rather as semantic pivot that provides for different ‘argumentation figures’ within the referential grid of the legal case

Fine structure and spin dynamics of excitons in the GaAs/AlxGa1-xAs superlattices

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Temperature behavior of hot carrier dynamics in InP quantum dots

Photoluminescence (PL) kinetics of the InP self-assembled quantum dots is studied under quasiresonant optical excitation in the temperature range 10–100 K. It is found that the PL rise time abruptly drops with increasing temperature. The model calculations based on the rate equations have shown that this drop cannot result from thermostimulated phonon relaxation of the hot carriers. We developed a model assuming that the main reason for variations in the PL kinetics is related to thermal ejection ("evaporation") of holes from the quantum dots, with a fraction of the dots acquiring negative charge. The model allowed us to describe quantitatively the PL rise as well as the PL decay over the whole temperature range under study. We identified also a number of effects caused by electron evaporation from the quantum dots at temperatures above 60 K. Comparison of the results of the model calculations with the experimental data has allowed us to determine rate parameters of the ejection processes

Two stage pressure-induced Yb valence change in the Hexagonal Laves Phase YbAg2_2: Investigation by time differential perturbed angular γ\gamma-γ\gamma correlation spectroscopy method and density functional calculations

We have studied the C14 hexagonal Laves phase of YbAg$_2$ at normal conditions and under external pressure up to 19 GPa by the time-differential perturbed angular $\gamma-\gamma$ correlation spectroscopy (TDPAC) using $^{111}$Cd probe nuclei. Under pressure the valence of Yb undergoes a two stage transition from 2.8 to 3. The two stage scenario is characterized by two distinct quadrupole frequencies of $^{111}$Cd probes in silver sublattice, monotonically increasing with pressure and saturating at 8 and 16 GPa. Our experimental data are compared with the density functional studies of the electron band structure of YbAg$_2$, whose results are used for discussion and interpretation of these experiments. We have found that there are two different electric field gradients at inequivalent silver sites and that $4d$-states of silver participate in metal bonding, allowing for the formation of the hexagonal Laves phase

Anti-Stokes photoluminescence of InP self-assembled quantum dots in the presence of electric current

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