Condensed Matter Physics
Emilio Cobanera Research
For the most part, the world is made of Atoms and Light. There are different flavors of Atoms, but not that many really. Humans know of exactly 103 different kinds of Atoms. A not-to-basic Lego game has more pieces than that! Nonetheless, the incredible variety of the world around you, water, ice, rocks, metals, plastic, magnets, fire, life, consciousness, is the manifestations of the incredible variety of complex ways atoms can come together. What is the magic trick that starts with 103 building blocks and glue (that is the role of Light) and builds out of it a myriad of materials and something far more complicated, yourself?The answer is that many atoms put together are more than the sum of the parts. Physicist called that idea, the idea that the total is more than the sum of its parts, emergent phenomena.
I am a theoretical condensed-matter physicist. That means I use ideas and mathematics to investigate emergent phenomena. If my work leads to a prediction about Nature, typically, the properties of some material or another at low temperatures, I look for an experimental physicist to help me test my prediction with an experiment. I focus most of my research effort on the theory of topological quantum materials. Let me start with an example. If you heat up a magnet enough, you will see that its magnetic properties go away. The reason is that a magnet is magnetic because there is magnetic order in the material. By heating it up, you disorder it and loose the magnetic properties. For many years people thought that all properties of materials could be understood as some kind of order in the material: loose the order, loose the property. This is true broadly speaking but there exist very counter-intuitive orders that are nothing like magnetism. To investigate these orders, one needs tools from a mathematical discipline called topology and a branch of physics called quantum mechanics. Topological quantum order is hard to understand but is also incredibly useful. For example, the best device in the world for measuring electrical resistance uses precisely one example of topological quantum order, the integer quantum Hall effect, to achieve mind-blowing precision. Topological quantum materials could also become the gateway to far more powerful computers. And it all starts with 103 Atoms and Light.
Caption
Sometimes, topological quantum order is revealed by transport measurements, that is, measurements of resistance. Here you can see the resistance of a device made of layers of Lanthanum Aluminate meeting layers of Strontium Titanate. Either the top row or the bottom row shows experimental data. Can you tell which one is which? From my paper M.Diez et. al., Phys. Rev. Lett. 115, 016803 (2015).
