2D Tin May be the New Graphene

Get ready physics fashion watchers (I hope you exist), because we’ve got a new exotic material to play with: stanene! If you know the roots of the element symbols, you may already know what this material is: a 2D sheet of tin. (In Latin, tin is stannum, and many words about tin compounds were derived from this. And it’s also why tin’s symbol is Sn.) The -ene comes from naming it in analogy to graphene. (And hopefully the name won’t get confused with the class of tin-containing organic compounds called stannenes that I found by adding an extra n in my Google search)

What makes stanene special? It is a special kind of material called a “topological insulator”. A pretty advanced discussion of topological insulators and the origin of their behavior can be found here. The main thing to know about topological insulators is that their name is a bit confusing; they can actually be great conductors of electricity.The bulk of a topological insulator is insulating, but at the surface or edges, electricity can flow.  (Three semesters of materials science is teaching me that surfaces are magical places.) Recent work has even managed to image that current and show it does indeed only flow at the edges.

Many of the topological insulators seem to have other special properties as well. Mercury telluride is a topological insulator that transports electrons in different electrons based on their spin, which could be very useful for spintronics and quantum computers. At its edges, stanene is a perfect conductor (although notably they don’t use the term superconductor), which means it doesn’t heat up as current flows through it. That waste heat represents lost energy. If you’ve ever felt a hot computer or smartphone, you can guess that a decent portion of the energy we use to power our electronics ends up heating them as well. This means stanene circuit components should need less power.

I originally thought graphene was also superconductive, but you need to modify it pretty specifically, so stanene may beat it out for electronics applications. What’s particularly important about stanene is the temperature at which the perfect conductivity is observed. Pure stanene still shows perfect conductivity at room temperature, which isn’t true for the bulk superconductors or other topological insulators we’ve currently made (even graphene). And adding fluorine to the stanene keeps it perfectly conductive  up to the boiling point of water! This means it could be used in nearly any consumer electronic.

Considering there is already talk of graphene being overhyped, some may wonder if a breakthrough like this could be the first nail in a hypothetical science coffin. It may be. I think this is going to be the start of a trend of many fantastic-seeming 2D materials. We’ve only recently discovered how to make graphene, and we’re just beginning to make other 2D materials (stanene being one of them). Part of the wonder of graphene came from decades of theoretical work preceding its creation in a lab; we knew a lot of the interesting properties it should have. But there isn’t as much history for many other 2D materials. And it also just seems like there’s a lot of special properties that come from materials only having 2D hexagonal structures. We are just beginning to come to a broader understanding of 2D materials, and I think this means we’re going to discover lots of plain materials have interesting properties in 2D along the way. It’s an exciting time.

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