Ross McKenzie, blogger of Condensed Concepts, is working on a forthcoming book, a Very Short Introduction about condensed matter physics. After reading some sample chapters, his son posed some questions about the field, and Prof. McKenzie put forward some of his preliminary answers here. These are fun, thought-provoking topics, and I regret being so busy writing other things that I haven't had a chance to think about these as much as I'd like. Still, here are some thoughts.
1. What do you think is the coolest or most exciting thing that CMP has discovered?
Tricky. There are some things that are very intellectually profound and cool to the initiated that would not strike an average person as cool or exciting. The fractional quantum Hall effect was completely surprising. I heard a story about Dan Tsui looking at the data coming in on a strip chart recorder (Hall voltage as a function of time as the magnetic field was swept), roughly estimating the magnetic field from the graph with the span of his fingers, realizing that they were seeing a Hall plateau that seemed to imply a charge of 1/3 e, and saying, jokingly, "Quarks!" In fact, there really are fractionally charged excitations in that system. That's very cool, and but not something any non-expert would appreciate.
Prof. McKenzie votes for superconductivity, and that's definitely up there. In some ways, superfluidity is even wilder. Kamerlingh Onnes, the first to liquefy helium and cool it below the superfluid transition, somehow missed discovering superfluidity, which had to wait for Kapitsa and independently Allen in 1937. Still, it is very weird - fluid flowing without viscosity through tiny pores, and climbing walls (!). While it's less useful than superconductivity, you can actually see its weird properties readily with the naked eye.
2 comments:
Maybe not "cool" like the collective behaviors you and McKenzie describe, but in terms of "profound" and "important," I would propose semiconductivity. The fact there are materials in which a seemingly fundamental property, electrical conductivity, can change by orders of magnitude in response to light, voltage, or ppm levels of impurities affects our lives in so many ways that we hardly notice it any more.
Similarly, the conceptual framework of band theory that makes this all seem natural is taken for granted.
Band structure in general is amazing. As I've written before, it's fascinating that periodic lattice = momentum-like conservation = dial-able relationship between energy and momentum = usual stuff as well as various exotic dispersion relations theorized in high energy contexts but only observed in solids. Then we can add in topology and interactions....
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