Friday, April 5, 2019

What is condensed matter physics?

How would you answer this question if you were asked by a non-expert who likes to learn and understand new things?
For example, a smart high school student, your uncle who reads a lot of popular science, an academic colleague in sociology, an economics graduate, ...
A draft of my answer is here.
I welcome suggestions for improvements.
Feel free to try it out on people you know who might be interested.


  1. Suggestion: consider glasses and/or plasma rather than commenting on the different phases of ice?
    I feel the ice does not get across as most people don't know this, and it appears to confuse phases of matter with condensed phases of a material?

  2. I remember the answer a friend of mine, a very well-known condensed matter theorist, gave his parents when they asked. He said, and I paraphrase: "Well, you know astronomy, the study of very distant objects like stars. That's the science of the very big. And you've heard of electrons and atoms and maybe quarks. That's the science of the very small. Condensed matter physics is everything in between"

  3. Somewhat related to the comment of pcs, I suggest that you explicitly point out the difference between the popular conception of phases of matter (as being defined only by rigidity and whether a substance fills its container) and the more general definition used in CM. The example of graphite and graphene is a nice one, another good one that everyone is intuitively familiar with is magnetized vs unmagnetized iron.

  4. Some comments:

    At room temperature diamond is actually an *amazing* thermal conductor. I think it is difficult to compare thermal conductivities of samples unless you can characterize the microstructure and vacancies. I bet that diamond's amazing thermal conductivity is because it grows with a low number of defects and lacks grain boundaries and twinning.

    With just a multimeter you can't measure resitivitity. You will measure resistance. You also need to know the sample geometry to convert it to resistivity.

    The standing ovation example is a very good example of collective phenomena! I've never heard this one before.

    Graphene wasn't discovered in 2004. It was known since the '60s. I'd say it was isolated and characterized in 2004 (you do say this a few sentences later), which actually gives more credit to the experimentalists.

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