More on polaron theory history

A recent Readers’ Forum section (Physics Today, April 2015, page 10 ) contains a discussion by Mark Dykman and Emmanuel Rashba about my review (October 2014, page 54 ) of Polarons by David Emin and about some aspects of the early days of polaron theory.

The term “polaron” was indeed coined by Solomon Pekar. ^{1 , 2} I agree that Pekar’s coinage is sometimes overlooked in the literature.

The development of the polaron concept was a gradual process initiated by Lev Landau. Pekar recognizes in his monograph ³ that “in 1933, L. D. Landau proposed an important idea on the auto-localization of an electron in an ideal crystal as a result of a lattice deformation by the field induced by the electron. These local states were assumed to be immobile, and Landau tried to associate them with F-centers in colored alkali halide crystals.” I think it is fair to state that all successive steps on polaron physics emerged from Landau’s first step.

For my book review, I found it unnecessary to write a more detailed introduction, and I limited the historical remarks on the polaron concept to the initial contributions of Landau. He introduced the nascent concept to Herbert Fröhlich, ⁴ who, in turn, introduced the commonly used basic polaron Hamiltonian for the continuum approximation to Jiro Yamashita, Theodore Holstein, and others, who laid the foundation of small-polaron theory.

Given the context of a short book review, I think not mentioning Pekar’s coinage of “polaron” and his important contributions does not constitute a major omission, as Dykman and Rashba suggest. In a different context—in a book or a review article—Pekar’s work would be amply cited. For example, reference contains a section devoted to Pekar’s polaron.