The European Physical Journal B (EPJ B)

2019 Impact factor 1.347

Condensed Matter and Complex Systems

EPJB Colloquium - How to understand real-world complexity through multiplex networks

Details: Published on 16 February 2015

An illustrative example of the multiplex network of nine nodes with two layers, the red solid) and the blue (dashed) layer.

Many real-world complex systems (from living organisms to human societies to transportation system) are best modeled by multiplex networks of interacting network layers. The study of multiplex network is one of the newest and hottest themes in the statistical physics of complex networks. Compared to single networks the current level of our understanding of multiplex networks is far from satisfactory. Pioneering studies have proven that the multiplexity has broad impact on the system's structure and function. Novel phenomena, unforeseen in traditional single-layer framework, can arise as a consequence of the coupling of network layers. In this EPJ B Colloquium Kyu-Min Lee, Byungjoon Min, and Kwang-Il Goh organize and review of the growing body of literature on statistical physics of multiplex networks by categorizing existing studies broadly according to the type of layer coupling in the problem. They discuss the recent major developments and point out some outstanding open challenges and research questions that warrant serious investigation, such as the identification of the minimal couplings (in the renormalization group sense) relevant to the characteristic discontinuous transitions in multiplex systems.

Kyu-Min Lee, Byungjoon Min and Kwang-Il Goh (2015),
Towards real-world complexity: an introduction to multiplex networks,
European Physical Journal B, DOI: 10.1140/epjb/e2015-50742-1

EPJ B Highlight - Probing qualities at the tips of nanocones

Details: Published on 01 February 2015

3D graphs of the local density of states with and without spin–orbital interaction for different distances r from the tip.

New understanding of electron behaviour at the tips of carbon nanocones could help provide candidates for use as a novel probe in atomic force microscopy

One of the ways of improving electrons manipulation is though better control over one of their inner characteristics, called spin. This approach is the object of an entire field of study, known as spintronics. Now, Richard Pincak from the Slovak Academy of Sciences and colleagues have just uncovered new possibilities for manipulating the electrons on the tips of graphitic nanocones. Indeed, in a study published in EPJ B, they have shown that because the tip area offers the greatest curvature, it gives rise, in the presence of defects, to an enhanced manifestation of a phenomenon called spin-orbit interaction. This, in turn, affects its electronic characteristics. These nanocones could thus become candidates for a new type of scanning probe in atomic force microscopy.

EPJ B Highlight - From stained glass to novel optical effect

Details: Published on 13 January 2015

Match-stick structure, consisting of a gold sphere (6 nm diameter) attached to a semiconductor nanorod (14 nm length). © J. Ebner *et al.*

Physicists investigate hybrid nanostructures made of semiconductor and metal components, yielding novel electronic and optical characteristics when exposed to light

Coloured stained-glass windows in churches typically contain metallic nanoparticles. They illustrate how light interacts with matter in a specific way at nanoscales. Depending on the material, different types of excitations arise within the inner structure of the material. By combining two different nanostructures, physicists expect the best electronic and optical response from each material. A team of Austrian scientists has just produced a model describing the optical properties of a matchstick-shaped hybrid nanoparticle, made of a cadmium sulphide semiconductor rod attached to a metallic gold cap. The results have been published in EPJ B by physicist Jakob Ebner and colleagues from the Karl Franzens University in Graz. Similar light-matter interactions have been observed in related systems, such as graphene. Better understanding such interactions could ultimately help in enhancing the sensitivity of chemical or biological detectors, as well as in increasing the efficiency of solar cells.

EPJB Highlight - Picosecond-range control over information processing

Details: Published on 12 January 2015

Energy levels of the parabolic QD versus the strength of the Rashba SOC. © J. A. Budagosky *et al.*

Optical manipulation is key to reaching the necessary speed to control the furtive underlying physical mechanism used in quantum information processing

Quantum computing will, one day, bring quicker information processing. One of the keys to such speed is being able to control the short-lived physical phenomenon holding quantum information, also known as quantum bits (qubits). A new study presents a novel optical manipulation technique to control one possible kind of qubit—represented, in this case, by polarised electron spins—exposed to an ultra-short pulsed laser in the picosecond-range. Jorge Budagosky and Alberto Castro from the University of Zaragoza, Spain, have tested this novel optics approach using a quantum dot—nanoscopic artificial structures with a small number of electrons—in a study published in EPJ B.

EPJ B Highlight - Winner and losers of the EU funding challenge

Details: Published on 10 December 2014

A representative Minimum Spanning Tree of the network of countries involved in the FP7 accepted proposals, which captures the backbone of interactions between the countries. © M.Tsouchnika *et al.*

Successfully attracting EU funding could depend on the nature of the research consortium

The European Union has a well-oiled funding mechanism in the form of grants given to research consortia. These are essentially made up of collaborating academic and industry-based research organisations. Understanding which type of consortium work receives funding could help future applicants. And it could also bring further transparency on how public funds are spent. Now, Maria Tsouchnika and Panos Argyrakis from the University of Thessaloniki, Greece, have brought valuable insights into the structure of research consortia that are most likely to attract EU funding, in a paper published in EPJ B.

EPJ B Highlight - When noise gets electrons moving

Details: Published on 02 December 2014

Realisations of harmonic noise. © D. V. Makarov *et al.*

A new study demonstrates the existence of a counter-intuitive current, induced by the sound-based equivalent of a laser, with applications in novel microscopic semiconductor devices

Studying the motion of electrons in a disordered environment is no simple task, mainly because given the effect occurring at the scale of interest—referred to as quantum scale—these electrons are otherwise impossible to examine, due to the presence of incidental phenomena. Often, understanding such effects requires a quantum simulator designed to expose them in a different physical setup. This is precisely the approach adopted by Denis Makarov and Leonid Kon’kov from the Victor I. Il’ichev Pacific Oceanological Institute in Vladivostok in a new study published in EPJ B. They relied on a simulator of electronic motion subjected to noise stemming from a flux of sound waves. These findings could lead to semi-conductor devices of a new kind, operated through acoustic radiations.

EPJ B Colloquium - Tensor network theory

Details: Published on 01 December 2014

Entropy of a 1d MERA: the number of links to cut in order to disconnect the L physical indices in the block form the rest of the system grows logarithmically with L, hence *S(L)* = O(log L). This is an example of an area-law in holographic space.

Tensor Network (TN) states are a new language, based on entanglement, for quantum many-body states. Román Orús, in a new EPJ B Colloquium, reviews four theoretical developments in TN states for strongly correlated systems.

EPJ B Highlight - Taming neural excitations

Details: Published on 25 November 2014

Spatio-temporal plots of complex space time patterns in excitable media. © C. Bachmair *et al.*

A theoretical study of short- and long-range effects on neural excitation pulses might one day lead to controlling harmful signals such as those in strokes

What do lasers, neural networks, and spreading epidemics have in common? They share a most basic feature whereby an initial pulse can propagate through a medium—be it physical, biological or socio-economic, respectively. The challenge is to gain a better understanding—and eventually control—of such systems, allowing them to be applied, for instance to real neural systems. This is the objective of a new theoretical study published in EPJ B by Clemens Bachmair and Eckehard Schöll from the Berlin University of Technology in Germany. Ultimately, with a better theoretical understanding, scientists aim to control such excitations in networks of neurons to prevent their detrimental effects like in stroke.

EPJ B Video - Competent Editorial Staff and Quick Handling System

Details: Published on 10 November 2014

Here's why you should publish your article on condensed matter or complex systems in EPJ B.

EPJ B Colloquium - Femto-nano-optics: ultrafast nonlinearity of metal nanoparticles

Details: Published on 05 November 2014

Pump-probe optical spectroscopy setup for single nanoparticle experiments

A deep understanding of the internal dynamics of metal nanoparticles, through the measurement of their time resolved optical response, requires detailed modeling of the physical processes involved. This EPJ B Colloquium explores the nonlinear ultrafast optical response of metal nanoparticles which can be obtained experimentally in ensembles and single nanoparticles, through femtosecond pump-probe spectroscopy.