Thursday, October 11, 2018

Key ideas in solid state physics

I have had some interesting discussions with an editor at Oxford University Press about the Very Short Introductions series. The upshot is that I have been asked to write a VSI Condensed Matter Physics. I find it amazing and concerning that after 500 titles there wasn't one about CMP. There are excellent ones on Magnetism, Superconductivity, Complexity, and Crystallography.
I am very happy about this and will post more about it later. At first, we discussed a VSI on Solid State Physics. Here is my outline for that.

1. Introduction
    Solid state physics
   - is central to technology (diodes, transistors, LEDs, photovoltaic cells, and computer memories)
   - provides important lessons in scientific model building
   - is one of the largest fields of physics
   - is a rich source of ideas and concepts that have cross-fertilised with other fields of science

2. Solids are quantum matter
Solids are made of atoms (nuclei and electrons).
Electrons are waves. Electrons are fermions. Quantum degeneracy
How is a metal like a white dwarf star?

3. Symmetry matters
Crystal structures. Think in reciprocal space, not in real space.
Why is it possible to determine a crystal structure from x-ray diffraction?
Internal symmetries of electrons: spin, gauge symmetries.

4. Electron waves in a crystal
Bragg scattering. Extended states.
Energy gaps: metals, semiconductors, and insulators
Why is copper a metal while diamond is an insulator?
Why can an electron go through a crystal and pass millions of atoms without being scattered?

5. Multitudes of solid phases
Phase diagrams. Allotropes.
When is graphite less stable than diamond?
Magnetic and superconducting phases
Classifications of phases through "broken symmetry"

6. Emergence
Quasi-particles: electrons and holes, phonons, magnons
How does structure (chemical and crystal) determines electronic and structural properties?
Why does magnesium seem to have positively charged electrical currents?

7. Beyond perfect infinite crystals
a. Impurities, disorder, localisation, glasses: the value of imperfection
b. Flatland. Surfaces and dimensionality

8. Topology matters
Quantum Hall effects, Topological insulators, Quantum magnetism

9. Solid state technology
 Diodes, transistors, LEDs, photovoltaic cells, and computer memories

10. Solid concepts
What have we learned about scientific model building?

This is too much. But what would you add or subtract?


  1. The VSI series is really excellent, and it would be great for you to write a Solid State Physics one. You've clearly outline something much longer than a VSI, though, as you said! I think that chapters 1-5 would make a solid (ahem) book, perhaps with chapter 9 added on. That book would include recent technological applications but not much in the way of recent advances in solid state physics. That's probably your safest bet, focusing on the strong foundations of the field and tying them to technologies.

    The desire to express where the field is now, though, is presumably why you put chapters 6-8 in the outline. Though I enjoy disorder myself, chapter 7 is the most obviously removable one. Chapter 6 strikes me as being a heavy lift for the target audience, as the concept of quasiparticle is, in my experience, quite hard to explain to people. Chapter 8 would be a good connection to modern research topics, but I don't know how easily/quickly you can actually get into those topics at the VSI level.

    Good luck!

  2. To me, chapter 8 looks the most cuttable. The interest and importance of topology comes well after the very short introduction stage!

  3. Just a couple of random thoughts:

    It seems that parts 2-5 could be condensed into two chapters, one about the crystal structure and the other one about electronic properties. As of now, part 2 introduces the concepts 3 and 4 expand on them and 5 kind of goes back to the things discussed in part 3.

    Bohr-van Leeuwen theorem could deserve a mention in the discussion of spin - another reason for quantumness to matter at macroscopic scales.

    Classification of phases through symmetry breaking (as a discussion of various phase transitions)seem to belong to the emergence part.

    I really like the idea of ending the book with a chapter about practical applications and a chapter about fundamental concepts that came out of the solid state physics.

    Best of luck with the book!

  4. I like the idea on the previous comment about a special mention of the Bohr-van Leeuwen theorem. “Magnetism is exclusively a quantum effect” is for me a surprising fact in CMP.
    Other fascinating ideas, that could go within “quasi-particles”, are fractionalisation and spin-charge separation.
    I don’t know about the length because I didn’t know about this collection, but the outline looks pretty complete.


  5. If the goal is to introduce condensed matter physics as a discipline, it may be worthwhile to emphasize universal concepts. For example, much is known about the topological theory of defects from work in liquid crystal and colloidal science. There are clear areas such as in 5, 6, and 7 where you can emphasize the breadth of condensed matter physics. I would also say that condensed matter is not limited to the solid state, so chapter 5 could be written about condensed phases in general.

  6. I will definitely get your book once it comes out!

    I think the outline is good, but I think that chapters 7 and 8 (especially 8) don't belong. A more general chapter about current research topics may work though.

  7. That looks like a reasonable outline for a solid state physics book. But if your remit is "condensed matter physics", that would call for a lot more. At least: nematic liquid crystals, polymers, colloids, surfactant phases and effective interactions in soft matter. Some of this would be common with the phase transitions/broken symmetry part of the solid state physics book. But I'd think that would be a bare minimum from a soft matter standpoint.

  8. What would you consider the most important experiments in solid state physics?

  9. Soft condensed matter is dealt by many including engineers. There is one big gap when they use surfactants. Many do not mention in papers how pure are the surfactants. This not mentioning of purity of surfactants appears repeatedly in many papers in very good journals. Please address this issue if you are writing about soft condensed matter as chapter.
    In good old days , pre neo-liberal era, many academics used to purify surfactants to maximum level and then do model studies. This has vanished now, because it takes time.

  10. This one published in Nature reported earlier by your blog is a classic case of an impurity being reported as the real substance.

  11. Thanks for all the helpful comments.
    I should clarify.
    I am not writing a VSI on Solid State but Condensed Matter. This was my solid state outline. I will post my CMP outline soon.