Graphene is a form of carbon in which the atoms are connected in a honeycomb structure. The possible ‘holy grail’ has this same structure, but is made of nanocrystals of mercury and tellurium. In their paper (, "Topological states in multi-orbital HgTe honeycomb lattices"), the theoretical physicists show that this material combines the properties of graphene with the qualities graphene misses. At room temperature, it is a semiconductor instead of a conductor, so that it can be used as a field-effect transistor. And it fulfils the conditions required to realise quantum spintronics, because it may host the quantum spin Hall effect at room temperature. Graphene, which was produced for the first time in 2003, is the first material discovered in which electrons move as if they have no mass. This is caused by the honeycomb structure of the Carbon atoms, which induces the electrons to behave as relativistic particles. However, it cannot realise the exotic quantum spin Hall effect, not even at very low temperatures. In their search for the holy grail, the challenge for the theoretical physicists was to find a way to shape a material that could have the potential to realise the quantum spin Hall effect at room temperature in a honeycomb structure. 
Honeycomb nanoribbon formed by the HgTe nanocrystals. Hg atoms are in yellow, Te atoms are in grey. The arrows along the ribbon indicate the electron propagation in the helical edge states present in the quantum spin Hall phase. Red and blue colours correspond to top and bottom edge for spin up, bottom and top edge for spin down, respectively. The quantum spin Hall effect, which was predicted in 1971, was only realised experimentally in 2006 by Prof. Laurens Molenkamp of the University of Würzburg and his team. They used mercury telluride/cadmium telluride quantum wells at a very low temperature. This inspired the theoretical physicists to design several honeycomb structures of mercury telluride nanocrystals and calculate their properties. Several structures turned out to have all the properties of the holy grail they were looking for. At Utrecht University, Prof. Daniël Vanmaekelbergh has already managed to synthesize this kind of honeycomb structures by using cadmium-selenide nanocrystals. “However, at the moment Prof. Laurens Molenkamp is the only expert in the world working with mercury telluride. So we are happy that he is very interested in synthesizing the honeycomb structures we designed with mercury telluride”, says Prof. Cristiane Morais Smith from Utrecht University. “Although it is not yet possible to realise it experimentally, he expects that the technology necessary will be available within a short time, given the developments that are going on in his lab right now. If we succeed in synthesizing it and the material indeed exhibits the unique combination of exotic properties at room temperature as we predicted, a field of fundamental research and technological innovations opens up that lies beyond our imagination.” For one thing, it could be used in spintronics, a technology that may be the next step in speeding up computers and the Internet. In spintronics, the electron ‘spin’ is used instead of the electric charge. Spin up and spin down are used to describe whether electrons rotate clockwise or counter-clockwise. If all electrons with spin up move to the left and all electrons with spin down to the right, then they create a spin current instead of an electric current. Spin currents can interact with nanomagnets and lead to applications in the context of fast reading and writing of magnetic memories..
Honeycomb nanoribbon formed by the HgTe nanocrystals. Hg atoms are in yellow, Te atoms are in grey. The arrows along the ribbon indicate the electron propagation in the helical edge states present in the quantum spin Hall phase. Red and blue colours correspond to top and bottom edge for spin up, bottom and top edge for spin down, respectively. The quantum spin Hall effect, which was predicted in 1971, was only realised experimentally in 2006 by Prof. Laurens Molenkamp of the University of Würzburg and his team. They used mercury telluride/cadmium telluride quantum wells at a very low temperature. This inspired the theoretical physicists to design several honeycomb structures of mercury telluride nanocrystals and calculate their properties. Several structures turned out to have all the properties of the holy grail they were looking for. At Utrecht University, Prof. Daniël Vanmaekelbergh has already managed to synthesize this kind of honeycomb structures by using cadmium-selenide nanocrystals. “However, at the moment Prof. Laurens Molenkamp is the only expert in the world working with mercury telluride. So we are happy that he is very interested in synthesizing the honeycomb structures we designed with mercury telluride”, says Prof. Cristiane Morais Smith from Utrecht University. “Although it is not yet possible to realise it experimentally, he expects that the technology necessary will be available within a short time, given the developments that are going on in his lab right now. If we succeed in synthesizing it and the material indeed exhibits the unique combination of exotic properties at room temperature as we predicted, a field of fundamental research and technological innovations opens up that lies beyond our imagination.” For one thing, it could be used in spintronics, a technology that may be the next step in speeding up computers and the Internet. In spintronics, the electron ‘spin’ is used instead of the electric charge. Spin up and spin down are used to describe whether electrons rotate clockwise or counter-clockwise. If all electrons with spin up move to the left and all electrons with spin down to the right, then they create a spin current instead of an electric current. Spin currents can interact with nanomagnets and lead to applications in the context of fast reading and writing of magnetic memories..
Rendering of the molecular structure of sodium disilicate glass. Researchers have identified a way to produce glass that is more durable. This means that over time, windows and digital screens can deform, eventually becoming unusable. In the case of cement, which has a molecular structure similar to that of glass, relaxation eventually leads to cracking and, in bridges and tall buildings, a loss of structural integrity. Mathieu Bauchy, an assistant professor of civil and environmental engineering at UCLA, and Matthieu Micoulaut, a professor of materials science at the Université Pierre et Marie Curie, have identified optimal conditions for developing more durable glass and cement. By performing computer simulations to test the molecular dynamics of materials commonly used to make glass, the researchers identified a range of pressures that are best for achieving “thermal reversibility,” in which a material will retain the same properties it had when it was produced, even if it has been exposed over time to variations in temperature. The research was published March 9 in ("Densified network glasses and liquids with thermodynamically reversible and structurally adaptive behaviour"). “The key finding is that if you use specific conditions to form glass — the right pressure and the right composition of the material — you can design reversible glasses that show little or no aging over time,” Bauchy said. Bauchy said the molecular structure of glass is analogous to the metal framework of the Eiffel Tower. Strength and rigidity are partially a result of the angles at which beams and crossbeams connect. The researchers’ new process improves the angles at which molecular bonds occur, making the material stronger. The research could also have a significant impact in slowing the production of greenhouse gases. The manufacture of cement and concrete results in approximately 5 percent of all greenhouse gas production, according to the American Ceramic Society. “The smaller the quantity of material we use to rebuild deteriorating structures, the better it is for the environment,” said Bauchy, whose research focuses on forging stronger ties between fundamental physics and engineering to design better, more sustainable materials. Bauchy was the lead author of the research; Micoulaut was the principal investigator.
Trefoil, Savoy, or simple … how do you fashion a “molecular” knot that has one of these shapes? Or better still, what are the most suitable “building blocks” for enabling the knot to assemble itself? So far, molecular knots have only been produced by chemical synthesis, obtaining constructs on an atomic scale. In the study coordinated by SISSA professor Cristian Micheletti, a team of researchers (from the Universities of Edinburgh and Padova as well as from SISSA) have tackled a previously unmet challenge: obtaining larger-scale knots starting from molecular building blocks with a specific shape and "sticky" ends allowing the fragments to assemble themselves spontaneously. Left free to move and interact in a solution, these fragments stick to one another to form complex three-dimensional units. How can we exploit this process to obtain a knot that has a specific shape? "It is necessary to study precisely the shape of the fragment", explains Cristian Micheletti, SISSA scientist and study coordinator. "So first we did that by using computer simulations and then we drew up a 'catalogue' of fragments for each use". The study simulated the self-assembly of differently shaped fragments interacting in a virtual solution, successively modifying specific parameters in the shape of the fragments. "This way we selected the most suitable shapes for assembling various types of knots" explains Micheletti.