Thursday, August 29, 2019

My tentative answers to some big questions about CMP

In my last post, I asked a number of questions about Condensed Matter Physics (CMP) that my son asked me. On reflection, my title ``basic questions" was a misnomer, because these are actually rather profound questions. Also, it should be acknowledged that the answers are quite personal and subjective. Here are my current answers.

1. What do you think is the coolest or most exciting thing that CMP has discovered? 



BCS theory of superconductivity.
Renormalisation group (RG) theory of critical exponents.

2. Scientific knowledge changes with time. Sometimes long-accepted ``facts''  and ``theories'' become overturned.  What ideas and results are you presenting that you are almost absolutely certain of? 

Phase diagrams of pure substances.
Landau theory and symmetry breaking as a means to understand almost all phase transitions.
RG theory.
Bloch's theorem and band theory as a framework to understand the electronic properties of crystals.
Quantisation of vortices.
Quantum Hall effects.

What might be overturned?

I will be almost certain of everything I will write about in the Very Short Introduction. This is because it centers around concepts and theories that have been able to explain a very wide swathe of experiments on diverse materials and that have been independently reproduced by many different groups.
I am deliberately avoiding describing speculative theories and the following.
Ideas, results, and theories based on experiments that did not involve the actual material claimed, involved significant curve fitting, or large computer simulations.
Many things published in luxury journals during the last twenty years.

3. What are the most interesting historical anecdotes? 

These are so interesting and relevant to major discoveries that they are worth including in the VSI.
Graphene and sellotape.
Bardeen's conflict with Josephson.
Abrikosov leaving his vortex lattice theory in his desk drawer because Landau did not like it.

What are the most significant historical events? 

Discovery of x-ray crystallography
Discovery of superconductivity.
Landau's 1937 paper.
BCS paper.
Wilson and Fisher.

Who were the major players?

They are so important that they are worthy of a short bio in the text.

4. What are the sexy questions that CMP might answer in the foreseeable future?

Is room-temperature superconductivity possible?


  1. Of your 5 great physicists 4 are theorists and all are white men. (These both seem to be common features of lists of great physicists.) It would be interesting to diversify the list a little.

    1. I find it quite ridiculous that the ethnicity or sex of a person should be relevant for their impact or importance.
      If I didn't know the first name, I wouldn't even know the sex of the person and I also don't care.

      That most are theoreticians might be a point to argue about. But in the end we want to `understand` Physics so we value the theory (which of course needs the experiment).

  2. Late Walter Kohn , a maths undergrad ,physics doctorate, DFT pioneer , CMP, won Nobel in Chemistry.

  3. Nothing about transistors?

  4. Fractional Quantum Hall Effect and new quasiparticles?

    High Tc?

  5. The methodology you have adopted by making your son an economics student ask questions about CMP could be the way of teaching in the coming years. Teaching has taken a backseat in Universities globally with heavy emphasis on research. One can paraphrase E Rutherford like this " All universities is research and the rest is all collecting pdf files" . You have given a very good way of teaching in a new way
    There is quote of the great Maxwell here which can also be paraphrased as "Thoroughly conscious ignorance is the prelude to every real advance in learning science or for the matter any subject.
    The original quote below here.
    “Thoroughly conscious ignorance is the prelude to every real advance in science.”

    ― James Clerk Maxwell