Optics and Magnetism in Two Dimensions
Marcos Guimaraes has been appointed on the first of February as Assistant Professor at the Zernike Institute of the RUG. In this capacity he will be dealing with two-dimensional materials and magnetism. “The purpose of my research is to better understand how the optical and magnetic properties of materials behave in two dimensions. This allows us to engineer new materials with specific properties. To build better computer memory, for example.”
Guimaraes is no stranger to Groningen. After his masters at the Federal University of Minas Gerais in his hometown in Brazil, he worked as a PhD student with Bart van Wees from 2010 to 2014. He then worked as a postdoctoral researcher at Cornell University in the United States. In the last two years Guimaraes worked as a researcher at Eindhoven University of Technology, funded by a NWO Veni grant. “At Cornell I familiarized myself with electrical methods to manipulate magnets (spin-orbit torque) and in Eindhoven with time-dependent magneto-optics, where we can measure the magnetization with time resolution. I will now combine the knowledge I gained in both places for my research here in Groningen.”
For his research, Guimaraes combines different two-dimensional materials; materials that consist of a single layer of atoms and thus have special properties. He does not only look at these layers separately, but stacks several layers on top of each other. Guimaraes compares it to a cake. “A cake consists of multiple layers: a layer of cake, a layer of whipped cream, another layer of cake, then a layer of chocolate, a layer of fruit and another layer of whipped cream, for example. All those individual layers taste differently when you combine them. And the beauty of it is that this allows you to make endless combinations. There are many different material 'flavours', which can have new unique features when they are put together. This is what makes working with two-dimensional materials so incredibly beautiful.”
Guimaraes’ research has two directions. “First and foremost, I’m interested in magneto optics: where we study how the intrinsic angular momentum of electrons (the spin) and magnetism behave using lasers. I am interested in the dynamics of these systems: how do they behave, how long these spins live in these materials, and how does magnetism behave in 2D? This gives us the opportunity to get to know the properties of two-dimensional materials better and better.”
The other direction is a more applied direction. “For this purpose, we use a ‘cake’ made of two-dimensional materials. On top of that cake we place a magnet. By running current through the layers, the outer layer of these materials can accumulate spins. They, in turn, can change the magnetization direction of the magnet on top. This change is permanent. These systems are therefore suitable for a new generation of memory devices, for example to improve the memory of computers."
Guimaraes enjoys working with two-dimensional materials because there are so many 'flavours'. “There are a lot of possible combinations which can lead to the discovering of interesting materials and different effects. But for the industry, it is difficult to manufacture these materials. On a small-scale level, we investigate which flavours are needed to yield interesting effects, and then we can attempt to make other materials which are industry-compatible but with the same characteristics."
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