Thursday, September 10, 2020

Emergence, surprises, and the future of condensed matter physics

 Where is condensed matter physics heading? Does it have a bright future? What are the big questions the field aims to (and might actually) address? What might we predict?

I need to address these kinds of questions in the last chapter of Condensed Matter Physics: A Very Short Introduction.

Here are three different perspectives.

1. Incremental advances.

We will continue to make advances on many fronts: chemical synthesis, device fabrication, experimental techniques, theory, computation, intellectual synthesis, connections with other disciplines, and technological applications. The basic intellectual structure of the discipline is in place. In the framework of Thomas Kuhn, it is "normal science" and we don't expect any "paradigm shifts." John Horgan provocatively proclaimed a quarter of a century ago that it is The End of Science.

2. Hype.

All of the forthcoming incremental advances will combine together to produce a revolution: materials by design. Suppose we want a material with specific properties, e.g., room temperature superconductivity with a high critical current density, and processible into durable wires.... We put this information into the computer and it will tell us the chemical composition, synthesis method, crystal structure, and material properties.

3. We don't know. Expect big surprises as we explore the endless frontier.

Condensed matter physics is all about emergent phenomena. By definition, emergent phenomena are hard to predict, even when you know many (or all) of the details of the system components and their interactions. They are often surprising. Sometimes we can explain (or at least rationalise) them a posteriori (after the fact) by rarely a priori

Just consider some of the long list of exotica from the past four decades: quantum Hall effects, many new classes of superconductors (heavy fermion, organic, cuprate, iron-based, buckyballs, cobaltates, ..), non-Fermi liquid metals, topological insulators, graphene, twisted graphene, colossal magnetoresistance, spin ices, macroscopic quantum tunneling magnets, superconducting qubits, ... Note that almost all of these were experimental discoveries first. Theorists may have had some inklings and broad suggestions of what to look for and where. However, that is quite different from there being consensus and expectation. For example, compare and contrast these discoveries with the case of the experimental discovery of the Higgs boson. It really wasn't that surprising and there was a strong consensus among theorists; both that it would be there and what specific properties it would have.

Perhaps, serendipity remains the best method of discovery.

What's next? Who knows?!

All I am game to predict is that CMP will continue to be an exciting discipline with many surprises and intellectual challenges.

What do you think?


  1. Ross, is outcome #2 really something that could be claimed by CMP? Many people in materials science or chemistry would broadly have similar aims and not consider themselves part of CMP. And then there are people who work hard on these kinds of problems and find it galling that "materials science" is a disciplinary name that appears to be extremely broad but where much of the work being done is not by people who would put themselves in that discipline.

    These kinds of discussion are always mainly semantics, so I offer them only as food for thought as you tackle the challenge of finishing your book!

    1. David, Thanks for the helpful comment. I agree completely with you. I put in #2 as an option, because this is what I sometimes hear people in CMP claim. However, I think it is just hype in a bid to get funding.It needs to be critiqued.I also don't think it is aim of CMP. Furthermore, it tends to be inconsistent with #3: emergent properties are hard to predict.

      I would say that CMP is a subset of materials science, not the other way around.

      Related issues are discussed here

      Please keep the great comments coming!

  2. What do you think of the "unsolved problems" currently listed in ?