Single-molecule junctions and atomic contacts

Dr. Laura Rincón made her thesis defense in August 2009. The manuscript, titled Conductance, thermopower and thermal conductance measurements in single-molecule junctions and atomic contacts, is a study on the properties of these contacts in the context of molecular electronics and thermoelectricity. The defense was recently awarded with the Best Experimental Thesis GEFES award.

Dr. Rincón used this picture we made years ago on request of her PhD advisor Prof. Nicolás Agrait.

One electron at a time, please

There is plenty of room at the bottom. Well, plenty, yes, but not infinite. There is a limit on how small we can build things, or something that happens to be of great technological importance: how faint an electrical current can be. And we might have just found an answer to that.

Researchers from the Max Planck Institute for Solid State Research in Stuttgart, Ulm University and the Autonomous University of Madrid, have found the most basic way of producing an electrical current. They’ve coupled two atomic energy levels and then measured the electronic transference between them, one electron at a time. We’re talking about single electrons here, folks! As it can be imagined, this presents a huge challenge: a fine tunned scanning tunneling microscope, low temperatures, crazy stability, pure skill in the sample preparation, etc. You can read the paper published in Nature Physics, or a more comprehensive explanation here.

In science we know how sterile it is to discuss the possible technological breakthroughs this research can bring. But this is of no importance here, because this research is just beautiful, and that is enough. This is about witnessing the quantum world at its most basic form, without ornaments. Do you know these simplistic pictures of energy levels with a wavy line connecting them? These people have made that picture real.

And talking about pictures, we made this one on request of Dr. Christian Ast and Prof. Carlos Cuevas, to illustrate not the experiment, but how they feel about it. And as an illustrator, that’s also beautiful.

Long live the Nucleobase!

Multiple medical and biological sensors and targeted drug delivery are based in the functionalization of nanoparticles (NPs) with biomolecules. The role of the NPs is to enhance the optical response of the target surroundings. But this enhancement comes with a huge risk: this same radiation can severily damage DNA or RNA producing mutations.

Johannes Feist (UAM) together with groups from the University of Modena and the University of Munich, have studied in which conditions these NPs can act as a protection for the biomolecules (in this case Uracil) while being effective in their sensing/therapeutic function. And importantly, the results proposed in their research can be easily implemented with the current nanophotonic technology.

This paper, published in the Journal of Physical Chemistry Letters, has been recognized with the cover we designed together with the supervision of Dr. Feist.

Polariton condensates’ propagation.

Polaritons are versatile quasiparticles that could be at the core of new technologies, since polariton devices have been proposed, such as polariton lasers, optical gates, transistors, spin-based elements and integrated circuits. Yet, their propagation depends strongly on the geometry of the pathway laid for them.

In a recent paper, Luis Viña, Dolores Martín, et al. in a huge collaborative research (Madrid, Jena, Würzburg, Saint-Petersburg, Reykjavik and Saint Andrews) have analyzed the Impact of the energetic landscape on polariton condensates’ propagation along a coupler”, published in Advanced Optical Materials.



The amount of technical challenges involved in this research is hard to grasp: from the manufacture of the guides to the experimental measurements, that require literally “taking pictures of light”.

We did this picture that was featured in the cover of Advanced Optical Materials, under close supervision of Dolores Martín and Luis Viña.

 

Living electric wires

Materials scientists have for decades fantasized about using DNA as a structural element in electronic circuits. And for decades, the electrical properties of DNA have remain a mystery. Hundreds of different, controversial results have appeared in the literature… That ends today!

Researchers from Jerusalem, Tel Aviv, Michigan, Cyprus, Seville and Madrid, have reported the observation of “very high currents of tens of nanoamperes” through the backbone of DNA molecules. And what it is more interesting, this conduction occurs through great distances.

This observation has required the development of several techniques: a way to “grow” DNA attached to a gold nanoparticle and a way to trap this DNA using non uniform electric fields. In fact, these techniques are important on their own and whey could be the base for the development of a novel electronic bio sensor, highly sensitive to specific sequences of DNA of RNA.

We made this picture for Prof. Juan Carlos Cuevas (UAM) to illustrate these results published in Nature Nanotechnology.

 

Age and friction

Friction between surfaces is of great importance and it is at the core of numerous and different phenomena: from earthquakes to the development of microelectromechanical systems. A new work involving Germany, Switzerland and Spain have studied how the role of contact aging affects this friction. In particular, they’ve shown how thermally activated bond formation dramatically changes the friction strength over time.

They’ve published their findings in Physical Review X and its work, together with an image we designed for them (with the close supervision of Dr. Guilherme de Vilhena) appears today (3/12/19) in PR-X featured papers.

Join the FTMC!

Condensed matter physics is a big unknown, even for 2nd year physics students, let alone theoretical condensed matter physics. And funny enough, this branch of physics covers a huge percentage of the reality around us. It covers quantum physics, biophysics, fluids, materials, optics and acoustics, or low temperatures, just to name a few of its interests. Yet, few people know about it.

At the Theoretical Condensed Matter Physics department, at Universidad Autónoma de Madrid are actively trying to fill this gap. They’ve made a video to inform and try to bring closer students and young people to this beautiful and amazing area of science. And Scixel happened to be around.

 

We’ve spend a great time working with them, discussing and creating this piece. Hope you like it and pay them a visit!

SAMS-4

SAMS-4 is the 4th edition of the Workshop on Scattering of Atoms and Molecules from Surfaces, which is organized every three years. Previous editions were held in Rehovot (Israel, 2010), Postdam (Germany, 2013) and Bergen (Norway, 2016) with great success. This year, organized by Prof. Daniel Farías the event will be held in Madrid.

Stefan Bilan kindly asked me to make a picture for their website. And this is what I did.

Cool, man!

[Sorry for the bad joke]

One of the issues of nanocircuits is heat dissipation. As in the macro world, at the nanoscale, it is imperative to find a way to cool circuits. Thanks to a collaboration between the University of Michigan and the Universidad Autónoma de Madrid, has been proved that a particular arrangement of molecules in nanocircuits, achieves and optimizes molecular termoelectric refrigeration.

This result has been published in Nature Nanotecnology.

Hammering viruses

Prof. Pedro de Pablo (Nanoforces Lab) has been using atomic force microscopy to break viruses for a while. Apart from the obvious pleasure that breaking things produces, their main focus is to study the stability of viruses. Viruses infect cells by releasing their highly packed genetic material. So the understanding of the stability of the viruses capsides will offer new venues for the development of novel antiviral strategies [article].