A. Nowak | Searcharxiv

arXiv2015

Ultrafast light-induced Coherent Optical and Acoustic Phonons in few Quintuple Layers of Topological Insulators Bi2Te3

Ultrafast lattice dynamics of few quintuple layers of topological insulator (TI) Bi$_2$Te$_3$ is studied with time-resolved optical pump-probe spectroscopy. Both optical and acoustic phonons are photogenerated and detected. Here, in order to get new insights on the out-of-equilibrium electron-phonon coupling and phonons dynamics in confined TI, different nanostructures have been investigated (single or polycrystalline QLs assemblies and nano-crystallized islands). Contrary to previous literature claims, we show that even for nanostructures containing only 10 quintuple layers (QLs), the symmetric A1g(I) coherent optical phonon is efficiently photogenerated and no restriction due to the structural confinement appears. We also observe that whatever the arrangement of the nanostructures, the A1g(I) optical phonon features are similar (lifetime). We also report the observation of confined coherent acoustic phonons propagating from QLs to QLs whose spectrum is, this time, very sensitive to the atomic arrangement. In the case of the single crystalline ultrathin film, the time of flight analysis of these acoustic phonons provides direct estimate of the elastic properties of these nanostructures as well as some estimates of Van der Waals interactions between QLs.

cond-mat.mtrl-sci↗

arXiv2013

Socio-inspired ICT - Towards a socially grounded society-ICT symbiosis

Modern ICT (Information and Communication Technology) has developed a vision where the "computer" is no longer associated with the concept of a single device or a network of devices, but rather the entirety of situated services originating in a digital world, which are perceived through the physical world. It is observed that services with explicit user input and output are becoming to be replaced by a computing landscape sensing the physical world via a huge variety of sensors, and controlling it via a plethora of actuators. The nature and appearance of computing devices is changing to be hidden in the fabric of everyday life, invisibly networked, and omnipresent, with applications greatly being based on the notions of context and knowledge. Interaction with such globe spanning, modern ICT systems will presumably be more implicit, at the periphery of human attention, rather than explicit, i.e. at the focus of human attention. Socio-inspired ICT assumes that future, globe scale ICT systems should be viewed as social systems. Such a view challenges research to identify and formalize the principles of interaction and adaptation in social systems, so as to be able to ground future ICT systems on those principles. This position paper therefore is concerned with the intersection of social behaviour and modern ICT, creating or recreating social conventions and social contexts through the use of pervasive, globe-spanning, omnipresent and participative ICT.

physics.soc-ph↗