Highlights

Every year, a committee of experts sits down with a tough job to do: from among all ICREA publications, they must find a handful that stand out from all the others. This is indeed a challenge. The debates are sometimes heated and always difficult but, in the end, a shortlist of 24 publications is produced. No prize is awarded, and the only additional acknowledge is the honour of being chosen and highlighted by ICREA. Each piece has something unique about it, whether it be a particularly elegant solution, the huge impact it has in the media or the sheer fascination it generates as a truly new idea. For whatever the reason, these are the best of the best and, as such, we are proud to share them here.

LIST OF SCIENTIFIC HIGHLIGHTS

Format: 2018
  • Seeing electrons surfing the waves of light on graphene (2017)

    Koppens, Frank (ICFO)

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    Researchers have studied how light can be used to “see” the quantum nature of an electronic material. They managed to do that by capturing light in a net of carbon atoms and slowing it down so that it moves almost as slow as the electrons in the graphene. Then something special happens: electrons and light start to move in concert, unveiling their quantum nature at such large scale that it can be observed with a special type of microscope. 

    The experiments were performed with ultra-high quality graphene. To excite and image the ultra-slow ripples of light in the graphene (also called plasmons), the researchers used a special antenna for light that scans over the surface at a distance of a few nanometers. With this near field nanoscope they saw that the light ripples on the graphene moved more than 300 times slower than light, and dramatically different from what is expected from classical physics laws. 

    The work has been published in Science by ICFO researchers Dr. Mark Lundeberg and Dr. Achim Woessner, led by ICREA Prof. at ICFO Frank Koppens, in collaboration with Prof. Hillenbrand from Nanogune, Prof. Polini from IIT and Prof. Hone from Columbia University. 

    In reference to the accomplished experiments, Prof. Koppens comments: “Usually it is very difficult to probe the quantum world, and to do so it requires ultra-low temperatures; here we could just “see” it with light and even at room temperature”. 

    This technique now paves the way for exploring many new types quantum materials, including superconductors where electricity can flow without energy consumption, or topological materials that allow for quantum information processing with topological qubits. In addition, Prof. Hillenbrand states that “this could just be the beginning of a new era of near field nanoscopy”. 

    Prof. Polini adds that “This discovery may eventually lead to understanding in a truly microscopic fashion the complex quantum phenomena that occur when matter is subject to ultra-low temperatures and very high magnetic fields, like the fractional quantum Hall effect” 

     

  • Randomness in quantum mechanics: philosophy, physics and technology (2017)

    Lewenstein, Maciej Andrzej (ICFO)
    Mitchell, Morgan W. (ICFO)
    Acín Dal Maschio, Antonio (ICFO)

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    This review contains the first interdisciplinary discussion of intrinsic randomness of quuantum mechanics, viewed from the contemporary point of view of quantum information science. In particular, this work covers recent developments in the area of quantum randomness, which is an extraordinarily interdisciplinary area that belongs not only to physics, but also to philosophy,
    mathematics, computer science, and technology. For this reasons the article contains three
    parts that will be essentially devoted to different aspects of quantum randomness, and even
    directed, although not restricted, to various audiences: a philosophical part, a physical part, and
    a technological part. Also for these reasons the article is written on an elementary level, combining
    simple and non-technical descriptions with a concise review of more advanced results. In this
    way readers of various provenances will be able to gain while reading the article.

     

  • The “DNA corrector” is more efficient in the most important regions of the genome (2017)

    López-Bigas, Núria (IRB Barcelona)

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    This work reveals that the mechanism that repairs errors in DNA is more efficient in the regions of genes that hold information for the production of proteins.

    The basic structure of genes is divided into exons and introns. The former holds the genetic sequences required to synthesize proteins, while most of the sequence of the latter hold less important information.

    When DNA is copied, the molecule called polymerase—responsible for replication—places one nucleotide after the other in the sister sequence following the original sequence, but from time to time the wrong nucleotide is incorporated, thus causing an error. These errors can be corrected by the DNA mismatch repair machinery.

    We showed that in tumors, with functional DNA mismatch repair machinery, exonic regions exhibit lower number of somatic mutations than expected. This decrease is not due to purifying selection. Instead, it can be explained by the enhanced activity of mismatch repair in exons compared to introns, a fact demonstrated by the lack of decrease in a type of paediatric brain cancer characterised by bialellic mismatch repair deficiency. The results of this work also suggest that the enhanced activity of mismatch repair in exons may be driven by the higher exonic levels of histone marks (H3K36me3).

    Mismatch repair system is conserved across evolution, which leads to the intriguing possibility that a combination of enhanced repair and purifying selection contributes to the observed lower exonic variation and divergence, both intra and inter-species. This has important implications for designing methods to study genic selection and for our understanding of the evolution of eukaryotic genes.

  • Efficient generation of energetic ions in multi-ion plasmas by radio-frequency heating (2017)

    Mantsinen, Mervi Johanna (BSC-CNS)

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    A new technique for the efficient generation of high-energy ions with electromagnetic ion cyclotron waves in multi-ion plasmas has been identified. These so-called ‘three-ion’ scenarios are especially suited for strong wave absorption by a very low number of resonant ions. To observe this effect, the plasma composition has to be properly adjusted, as prescribed by theory. The potential of the method has been demonstrated on the world-largest plasma magnetic confinement device, JET (Joint European Torus, Culham, UK), and the high-magnetic-field tokamak Alcator C-Mod (Cambridge, USA). The obtained results demonstrate efficient acceleration of 3He ions to high energies in dedicated hydrogen–deuterium mixtures. Simultaneously, effective plasma heating is observed, as a result of the slowing-down of the fast 3He ions. The developed technique is not only limited to laboratory plasmas, but can also be applied to explain observations of energetic ions in space-plasma environments, in particular, 3He-rich solar flares.

  • Towards quark matter from the fifth dimension (2017)

    Mateos, David (UB)

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    Quarks are the fundamental constituents of the protons and neutrons contained in the atoms that we and the things around us are made of. When quarks are compressed to the highest possible densities, even higher than those in atomic nuclei, the resulting form of matter is known as quark matter.

    Understanding the properties of quark matter is of great physical interest. A massive experimental effort is being devoted to this goal at particle colliders such as the Relativistic Heavy Ion Collider in Brookhaven (US) and at the Large Hadron Collider in Geneva (Switzerland). Moreover, quark matter may be naturally realized at the cores of neutron stars, the densest objects in the Universe, where gravity compresses quarks to densities that may be several times higher than those in atomic nuclei. The recent discovery of gravitational waves produced in neutron star collisions opens a new avenue for the study of the properties of quark matter.

    Despite its great physical interest, the theoretical study of quark matter by conventional, particle-physics methods is exceedingly difficult. For this reason, my group has resorted to a non-conventional method known as gauge/gravity duality.  The duality is a theoretical tool that maps the properties of quark matter in our four-dimensional world to those of … gravity in five dimensions! We have been able to build the first model in this context in which all the necessary ingredients are duly accounted for, and we have shown that it automatically incorporates several of the properties that quark matter is expected to have on general grounds. These results are hugely encouraging and open the door to a future understanding of quark matter from the fifth dimension.

  • Building new biosensors using graphene (2017)

    Merkoçi, Arben (ICN2)

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    Graphene related materials are attracting scientists from both academia and industry for their various advantages with interest for several applications. Among graphene forms graphene oxide (GO) and graphene quantum dots (GQDs) display advantageous characteristics with interest for building innovative biosensing platforms. This is due to their excellent capabilities ranging from easy linking to (bio)chemical/synthetic receptors to unprecedented electronic and optical properties. Quenching of the fluorescence induced by GO or photoluminescence of GQDs can easily operate in synergy with various other nanomaterials and platforms opening the way to several unprecedented biosensing strategies. In our recent publications we have explained the rationale behind the use of GO and GQDs in several optical and electrochemical biosensing technologies. Taking advantage of graphene materials we have developed simple, sensitive, selective and rapid biosensing platforms for various diagnostics applications. Coupling of graphene with simple green materials such as nitrocellulose is further pushing paper-based sensors toward cost efficient sensing technologies opening the way to future industrialization of such point of care devices with interest for human health protection, safety and security beside other uses.

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