What's So Interesting About Condensed Matter Physics?

If you go by physics-related stories in the mass media, you'd probably get the impression that about 90% of physicists work at the Large Hadron Collider or some other big accelerator lab. The other 10% would be dominated by people working on foundational questions in quantum mechanics-- Bell tests, teleportation, quantum information processing-- with a smattering of people doing something with superconductors. The distribution in the physics blogosphere is pretty similar.

And yet, if you went by the mass media impression, you'd be way wrong. The largest division of the American Physical Society by far is the Division of Condensed Matter Physics. According to the membership statistics for 2008, there are 5595 members in the Condensed Matter division, compared to 3474 in Particles and Fields, and 2837 in my own division of Atomic, Molecular, and Optical Physics. Condensed matter physicists outnumber string theorists and accelerator jocks by a huge margin.

Yet you hardly ever see media reports on condensed matter physics.

The reason for this is fairly obvious, which is that particle physics and quantum mechanics provide a much better "hook" for pop-science stories. It's relatively easy to explain why people are interested in high energy physics-- you've all heard it a million times. Studying matter on the most fundamental level, origin and fate of the universe, blah, blah, blah. Quantum mechanics is an easy sell as well-- it's just freakin' cool.

So, what's interesting about condensed matter physics?

There's got to be something there, after all, otherwise why would so many physicists go into that end of the business? There has to be something about condensed matter physics that grad students find interesting enough to choose it as a thesis area.

Beats me what it is, though. I took one semester of solid state out of Ashcroft and Mermin, and that was more than enough for me.

If I had to hazard a guess, though, it would be this: Condensed matter physics is good for stuff. It's the study of solids and liquids and their physical properties, and thus just about everything we deal with on a daily basis falls into the realm of condensed matter physics. It's about understanding the things we actually use and interact with.

Condensed matter physics is what allows us to understand the behavior of electrons in conductors and semiconductors, which lets us build computer chips and transmission lines. It's the branch of physics that underlies materials science, which lets us make stronger and lighter composite materials to build safer and more efficient cars and planes. It's where we find people studying superconductivity, which holds the promise of lossless power transmission and levitating trains, and all those nifty technologies that are twenty years off.

If you've had your life materially affected by something done by a physicist, odds are it was a condensed matter physicist.

And that's why they get no media play. Condensed matter physics just isn't cool. Condensed matter physics is practical, and practical is never cool.

Practical makes people's lives better, though. And practical gets people jobs. So maybe they don't need to be jealous of the high energy crowd, after all...

I would love to read an essay or blog post on "What's So Interesting About Condensed Matter Physics" from somebody in the field, though. I'd like to hear what drew all those thousands of people into the field in the first place. My guess about practicality is just that-- a guess. I'd love to hear from somebody who knows. Because for all I know, the people in the field really do believe that what they do is not just practical, but cool.

And if I knew why they find their field cool, I'd have a better appreciation of it. And if we all knew why they think it's cool, maybe we'd be able to see how to convey that cool to the New York Times and get them their fair share of media attention.

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There was a time in the 80's when Condensed Matter was prominent in the media for high-T superconductivity. Although other fascinating materials, with interesting phenomenon, have been discovered, there really hasn't really been that much progress to delivering those long promised levitating trains. Even last year's Nobel for GMR materials, and their role in data storage didn't gain that much media attention.

Well, just about all of the arguments you make for AMO in your next post apply to condensed matter systems as well - lab scale experiments, real things, useful technologies, etc. Looking at the superconducting QC community, there's even been a pretty big recent trend toward doing essentially AMO experiments in superconducting circuits (cavity QED -> circuit QED). So, condensed matter physics is cool because it now is a superset of AMO, obviously.

well, the most interesting things in condensed matter are not necessarily practical. I'm thinking here about the quantum Hall effect, specifically. You need huge magnetic fields and very low temperatures. But the observed effects are pretty striking. And the underlying dynamics of the electrons to produce those effects is very different from how we usually think of electrons.

In fact, the interesting features of quantum field theory are much more apparent in condensed matter than, say particle physics. I mean its called "particle" physics because these things are basically acting like particles, little localized lumps that run into each and maybe change species in the process. But you're not going to get much insight into the fractional quantum Hall effect by thinking in terms of single electrons. So I think its pretty neat from the theoretical side.

Well, as you know, what makes something "cool" for writing a puff piece in the NYT is not usually what makes something "cool" to work on. So, most of what I found cool about condensed matter research is not stuff that would make for a thrilling article in the mass media.

* Condensed matter experiments are small and (usually, comparatively) economical. I got to design, construct, run, and interpret the experiment all by myself, or as part of a small group of people. Rather than being a cog in a collaboration containing hundreds if not thousands of scientists, I get to feel like I'm making a substantial contribution.

* Condensed matter physics (at least some subsections of it) is relevant and relatable to the everyday world. I can't take inspiration for high energy physics from my breakfast, but I can wonder why are coffee stains darker at the edges, or how is it that all the big chunks of granola end up at the top of the carton, or how does a water drop break off from the dripping tap, and then go do some experiments to find out. For me, that embodies exactly what's cool about science in general: you see something, wonder how it works, and try to figure it.

* Being able to find a well-paying job outside of academia is nice, too. It means I can keep doing science, even thought I'm finished w/ grad school. And that is cool.

I am most of the time more amazed about the complex world we live in than the "simple" laws that drive it, that's why I think condensed matter is cool.

The boundaries of different science disciplines are starting to fade and condensed matter is at the front of this new approach. Reductionist thinking is becoming less useful when dealing with big systems of interacting things, be it a swarm of electrons in a metal, grains of sand, the economy or life itself. In all these systems news phenomena emerge from their collective behavior (superconductivity, Kondo effect,...), and the total is not just the sum of its parts. Within condensed matter is the true theory of "everything", if such a thing exists.

Condensed matter generally offers a lot more opportunities for interdisciplinary work than other physics sub-fields. Because it works with everyday objects and materials, collaboration is possible with biologists, chemists, materials scientists, engineers, etc. It's not just practical in an application-oriented sense, it connects to other sorts of scientists more easily.

So I think it's cool to work in condensed matter because I get to interact with interesting people outside my field pretty often, and learn about things outside "pure" physics. Cool to everybody else? That I can't answer.

As an outsider (nuclear physics, which I found cool because -- possible at the time -- I could run a cyclotron all by myself) I'd say both condensed matter and AMO don't emphasize enough the fundamental nature of the many-body and few-body quantum problems they explore. [The point made in #3.] Neither does nuclear physics, which has been co-opted by the glitz of particle physics in some sub-fields.

I also think condensed matter is way too apologetic for working on practical problems, as if applied physics isn't physics because it is getting close to engineering or might actually be used to make money. It isn't engineering until you can *train* someone to do it. Its physics when you make it up for the first time based solely on your intuition about how nature works.

By CCphysicist (not verified) on 09 Oct 2008 #permalink

My wife, Prof. Christine M. Carmichael, asked me to post this comment:

"You can tell Chad that the reason I thought condensed matter physics was cool was because unlike those other fields, I could build my own equipment, do the experiments while all alone in the lab, and pursue my own research without being a member of a huge team."

Cool? Most of it is f***ing freezing!

Superconductivity, supefluidity, Bose-Einstein condensates ...
There's a lot of interesting and fundamental(*) stuff going on in condensed matter physics and I agree it would be fun to learn more about it.

(*) By "fundamental" I mean "not reducible to the properties of its constituents".

Condensed matter physics is cool because it offers opportunities for interesting applications of statistical mechanics. Stat. Mech. being, as we all know, the coolest area of physics:)

By BiophysicsMonkey (not verified) on 10 Oct 2008 #permalink

Condensed matter is also cool because it has much more complicated problems than many other areas. As Wolfgang Pauli put it, "The surface was invented by the devil!" Safe in the interior of objects, atoms behave relatively predictably. But at the surface, just about all the simplifying assumptions break down and atoms do very weird, and very cool, things. The relatively recent introduction (and refinement) of Scanning Tunnelling Microscopes (and similar tech) is driving a lot of new research in that area.

There's an old joke my high school physics teach used to tell, about the different between a physicist and an engineer. A physicist is the type of person who takes his car completely apart to figure out how it works, then leaves the pieces scattered in the driveway while he goes inside for a beer. An engineer is the type who, while walking by the house, sees all the pieces scattered to hither and yon, and sits down to put his friends car back together again.

A Condensed Matter physicist lines up her parts nice and neat, with notes, grabs her beer, and then comes back out to help put the car back together.

Personally, it's really cool to ask "ok, what happens when you have more than one?" For experimental cm physicists, I think it's the idea of asking "what happens when I do this?" on an experiment that is only a few steps removed from cooking in your kitchen. Plus, we really are excited about the fact that a bucket of water is just as interesting, if not more so, than a huge collider...

Re #8, my wife is too modest (unlike myself, a tireless self-promoter). Her Postdoc work at UNSW in Sydney, Australia, was driven by the fact that there was only one MBE (Molecular Beam Epitaxy) machine in the whole Oz continent, and her group could get at most an hour per month with it.

To make gallium arsenide thin film without that, what could she do? Melting some GaAs and dipping the substrate in it would be uneven in thickness and quality, and easily contaminated. Reducing Arsine (AsH4) and gaseous gallium to chemically combine onto the substrate would be, well, Arsine is fatal if breathed in a concentration of one part in a million.

She heard that U. Illinois had a 4th approach, so flew to the USA and met with that department. Then she flew back to Sydney and cobbled together an improvised apparatus for under $10,000 plus used miscellaneous equipment. She made high quality thin film GaAs by ion sputtering.

When we met (at the Aussiecon) she had a dozen other postdocs sharing her hacked-together equipment, getting great results, and publishing happily.

When she came to the USA she improvised further, making a superlattice (alternate layers of this and that) including GaAs on a diamond substrate. The US Government concluded that the 3 highest quality thin film GaAs laboratories were those of "IBM, Bell Labs, and Dr. Christine Carmichael."

She thinks that the LHC is good (and we published our predictions years ago) but she iterates that being able to make your own stuff on your own devices, and analyze the data yopurself, is muich nicer than the vast expenses and politics and experiment lengths of "big science."

That leaves her time to write good science fiction, teach classes, and be a first rate wife and mother.

Yay, condensed matter physics!

>And if I knew why they find their field cool, I'd have a
>better appreciation of it. And if we all knew why they
>think it's cool, maybe we'd be able to see how to convey >that cool to the New York Times and get them their fair >share of media attention."

Interesting comments Chad. I've had some thoughts on this ... Due to laziness I'll just give the link to my (hopefully still relevant) spiel regarding this point on Jennifer Ouellette's blog.


Few things/corrections:

1) Condensed matter physics (CMP) is not "necessarily" practical
2) Quantum mechanics(QM) cannot be isolated from Condensed matter Physics.

Personally, if I am asked - why is CMP cool? I will most likely look at my own area of work and explain.

I do mesoscopic physics. I get to see the macroscopic manifestation of some microscopic properties (read: Quantum mechanics) in lab. So, ain't that cool?! :)

I really like Prof. Doug Natelson's blog on various topic in CMP: http://nanoscale.blogspot.com/