- Published on 07 March 2017
Physicists define a smart way of inducing large-amplitude vibrations in graphene models, which could open the door for novel electronic applications
Graphene, the one-atom-thick material made of carbon atoms, still holds some unexplained qualities, which are important in connection with electronic applications where high-conductivity matters, ranging from smart materials that collectively respond to external stimuli in a coherent, tunable fashion, to light-induced, all-optical networks. Materials like graphene can exhibit a particular type of large-amplitude, stable vibrational modes that are localised, referred to as Discrete Breathers (DBs). The secret to enhancing conductivity by creating DBs lies in creating the external constraints to make atoms within the material oscillate perpendicular to the direction of the graphene sheet. Simulations-based models describing what happens at the atomic level are not straightforward, making it necessary to determine the initial conditions leading to the emergence of DBs. In a new paper published in EPJ B, Elham Barani from the Ferdowsi University of Mashhad, Iran, and colleagues from Russia, Iran and Singapore use a systematic approach to identify the initial conditions that lend themselves to exciting DBs in graphene, ultimately opening the door to understanding the keys to greater conductivity.
EPJ B Highlight - Tortoise electrons trying to catch up with hare photons give graphene its conductivity
- Published on 14 December 2016
Collective electron interaction, mediated by photons across space-time under a weak magnetic field, explains the special conductivity of the one-atom-thick material
How electrons interact with other electrons at quantum scale in graphene affects how quickly they travel in the material, leading to its high conductivity. Now, Natália Menezes and Cristiane Morais Smith from the Centre for Extreme Matter and Emergent Phenomena at Utrecht University, the Netherlands, and a Brazilian colleague, Van Sergio Alves, have developed a model attributing the greater conductivity in graphene to the accelerating effect of electrons interacting with photons under a weak magnetic field. Their findings have been published in EPJ B.
- Published on 09 November 2016
Tweaking equations to drive greater superconductivity-inducing crystal vibrations proves theoretical possibility of creating higher temperature superconductors
Superconductivity is like an Eldorado for electrons, as they flow without resistance through a conductor. However, it only occurs below a very low critical temperature. Physicists now believe they can enhance superconductivity - the idea is to externally drive its underlying physical phenomena by changing how ions vibrating in the crystal lattice of the conductor material, called phonons, interact with electron flowing in the material. Andreas Komnik from the University of Heidelberg and Michael Thorwart from the University of Hamburg, Germany, adapted the simplest theory of superconductivity to reflect the consequences of externally driving the occurrence of phonons. Their main result, published in EPJ B, is a simple formula explaining how it is theoretically possible to raise the critical temperature using phonon driving.
- Published on 04 November 2016
The Ψk conference is the foremost event in the field of electronic structure and computation in condensed matter, and the Volker Heine award is one of its highlights. Being intended for young researchers, the award aims at helping their career by exposing their work in a prestigious international conference, and adding a modest point to their Curriculum Vitae.
- Published on 04 November 2016
First-principles calculations combining density functional theory and many-body perturbation theory can provide microscopic insight into the dynamics of electrons and phonons in materials. In this EPJ B Colloquium, Marco Bernardi, winner of the Psi’K young investigator award, reviews this theoretical and computational framework, focusing on perturbative treatments of scattering, dynamics, and transport of electrons and phonons. The article examines applications of these first-principles calculations in electronics, lighting, spectroscopy, and renewable energy.
- Published on 25 October 2016
Supersonic solitary waves in nano-electronics crystals show potentials for electric charge or matter transport and energy storage with extremely low heat dissipation
Freak waves, as well as other less striking localised excitations, occur in nature at every scale. The current theory and models of such waves can be applied to physics and, among others, to oceanography, nonlinear optics and lasers, acoustics, plasmas, cosmological relativity and neuro-dynamics. However, they could also play a significant role at the quantum scale in nano-electronics. In a recent study, Manuel G. Velarde from the Pluridisciplinary Institute of the University Complutense of Madrid, Spain, and colleagues, performed computer simulations to compare two types of localised excitations in nano-electronics. Their findings, published in a recent study in EPJ B, confirm that such localised excitations are natural candidates for energy storage and transport. These, in turn, could lead to applications such as transistors with extremely low heat dissipation not using silicon.
- Published on 09 August 2016
Stabilising materials with transient magnetic characteristics makes it easier to study them
Magnetic materials displaying what is referred to as itinerant ferromagnetism are in an elusive physical state that is not yet fully understood. They behave like a magnets under very specific conditions, such as at ultracold temperatures near absolute zero. Physicists normally have no other choice than to study this very unique state of matter in a controlled fashion, using ultracold atomic gases. Now, a team based at ETH Zurich, Switzerland has introduced two new theoretical approaches to stabilise the ferromagnetic state in quantum gases to help study the characteristics of itinerant ferromagnetic materials. These results were recently published in EPJ B by Ilia Zintchenko and colleagues.
- Published on 06 July 2016
New theoretical approach to understand the dynamics of populations reaching consensus votes or of spreading epidemics
Social behaviour like reaching a consensus is a matter of cooperation. However, individuals in populations often spontaneously compete and only cooperate under certain conditions. These problems are so ubiquitous that physicists have now developed models to understand the underlying logic that drives competition. A new study published in EPJ B shows the dynamics of competing agents with an evolving tendency to collaborate that are linked through a network modelled as a disordered square lattice. These results are the work of Chen Xu from Soochow University, Suzhou, China and colleagues. They believe that their theoretical framework can be applied to many other problems related to understanding the dynamical processes in complex systems and networked populations, such as the voter dynamics involved in reaching a consensus and spreading dynamics in epidemic models and in social networks.
- Published on 22 June 2016
Surface phenomena in ring-shaped topological insulators are just as controllable as those in spheres made of the same material
Topological insulators behave like insulators at their core and allow good conductivity on their surface. They owe their characteristics to a new quantum state within the material discovered in 2007 and 2009 for 2D and 3D materials, respectively. Scientists studying the surface of ring-shaped, or toric, topological insulators, have just discovered some characteristics that had only previously been confirmed in spheres. Jakson Fonseca from the University Federal of Viçosa, Brazil, and colleagues describe their findings in a paper published in EPJ B. These results could hold considerable potential for applications in electronics. Indeed, this discovery means that the curved surface induces internal fields, called gauge fields, in the electrons carrying the electric charge located at the surface. By contrast, in graphene, similar fiels have been induced by mechanical tensions or defects in the way the carbon atoms are arranged in the one-atom-thick honeycomb lattice.
- Published on 23 March 2016
Peering into the future of populations with the help of complex networks of predictive maps
Predicting the future from the present - that’s what logistic maps can do. For example, they can be used to predict the evolution of a population in the near future based on its present situation. They are relevant when studing systems such as entire populations, where the behaviour of the separate units - which have the ability to self-organise - cannot explain the behaviour of the system as a whole. Alexandre L'Her from the University of the Republic, Montevideo, Uruguay, and colleagues have now developed an electronic version of a logistic map that is capable of interacting with many other maps, making the model scalable. As a benchmark to explain new emerging behaviours of entire complex systems, they have studied networks of logistic maps coupled together at various levels. Their findings were recently published in EPJ B and make it possible to more easily compare previous computer simulations with experimental results obtained using this state-of-the art electronic model.