Why Condensed Matter?

Computational PhysicsCondensed Matter Physics
Written By Mackenzie Seal

Condensed matter is unlikely to be discussed as a cocktail conversation. I can’t say I’ve attended a party, and, while mingling, someone has asked me a question about the atomic structure of materials or about solid state devices (though I’ll declare it a possibility that maybe I just haven’t attended the right parties). More often than not, conversations lead to questions on the latest SpaceX launch or the Big Bang. 

The draw of rocket science and astrophysics seems natural, especially with the success in both fields in recent years. With the release of the Nobel Prize-winning image of a black hole, celebrity astrophysicist Neil DeGrasse Tyson’s StarTalk Radio, and whatever Elon Musk is posting on Twitter, the space industry stays trending.

I can’t blame people for not having a hobbyist interest in condensed matter, especially when the name of the field itself is ambiguous. Google’s top four “People also ask” about Condensed matter are:  What is meant by condensed matter physics?, What do condensed matter physicists do?, What is condensed state of matter?, and Is condensed matter physics hard?

You likely won’t cover it in Physics I, and there are less than 1000 Instagram posts #condensedmatter versus almost 800,000 posts with #astrophysics. 

So what is Condensed Matter?

Condensed matter is the study of macroscopic and microscopic properties of matter in the “condensed phase” (liquids and solids, due to their particles being close together). Macroscopic refers to physical properties of matter that can be observed with our eyes, i.e. density, viscosity, shape. It follows that microscopic properties are properties that we cannot see — how atoms and electrons are interacting. Condensed matter physicists build models to correlate the physical properties of matter and their atomic interactions. 

How atoms are arranged or manipulated affect their physical properties — take for example, diamond and graphite. Diamond is the hardest mineral known to man; graphite is on the opposite end of the Mohs Hardness Scale. Additionally, diamond is an electrical insulator (graphite is a conductor), transparent (graphite is opaque), and valuable (graphite is so cheap, it’s used to make pencil lead). Yet, both are crystalline forms of the same element, carbon. 

The difference between them is due to the atomic structure differences — graphite forms sheets of carbon atoms and has strong bonds on the same layer, but weak bonds between layers. In contrast, carbon atoms in diamond are closely packed and have strong bonds in three dimensions. 

Understanding these differences is a key role for condensed matter physicists, but their studies are not limited to just crystallography, but range across a variety of topics including superconductivity, topological materials, and quantum computation to name a few. 

What is Computational Physics?

I work in the computational side of condensed matter — my “lab” consists of computers. In my research group, we build mathematical models of condensed matter systems on a computer and simulate it under various conditions. These calculations even for a simple material cannot be solved with pen and paper and require high performance computing clusters to aggregate computing power to perform such calculations. A cluster is basically several computers centrally connected and controlled by software.  

Computational physics complements traditional theoretical and experimental research. Often computational physicists collaborate with experimentalists, and use experimental data to refine models. However, generating models is typically not the only role of a computational physicist — they also may develop mathematical formalism to apply to computational protocols or other more “pure” theoretical projects.

Computational physics is just as broad as theoretical and experimental branches of physics, and spans across nearly all modern research topics, from statistical mechanics to biophysics. 

Why do I study it?

I came into computational physics due to my love of and interest in computers, coding, and machine learning. It was a natural step for me in my career and personal development.

My relationship with condensed matter was developed — I probably was one of those who Google’d “What is Condensed Matter” prior to entering my Master’s program. I consider this field to be underrepresented in science communication, especially considering it is the most active field of contemporary physics, accounting for nearly one third of all American physicists.

While it may be the most active field of research in the U.S., there is so much we don’t know yet. And, when we make a discovery, often, there are direct impacts to our world. Systems in CM can be manipulated; we are not just observing what is there, we engage with the materials. As members in our society, we are the end users and only receive the products developed based on the successes in condensed matter. These successes are often invisible to us — we have our cell phone which represents hundreds of different materials that had to be discovered and tuned in order to produce such a device.

It is estimated we know less than 1% of material compounds in the world. In order to continue to revolutionize our technology, we must continue to investigate materials. Using computational methods in condensed matter helps speed up material discoveries and provides a road map for material and device design.

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Mackenzie Seal