Tuesday, March 6, 2012
The beauty of the Drude model
I have been teaching the Drude model for the umpteenth time, but have a new slant I am emphasizing to the students. It only involves a single new parameter, the scattering time. Yet it is able to capture the details of a wide range of experiments on elemental metals. I think it is important for students to appreciate the importance of considering the simplest possible models, with as few free parameters as possible, and see what they can and cannot explain. Only then one should move to more advanced models which are closer to the "truth".
Subscribe to:
Post Comments (Atom)
From Leo Szilard to the Tasmanian wilderness
Richard Flanagan is an esteemed Australian writer. My son recently gave our family a copy of Flanagan's recent book, Question 7 . It is...
-
Is it something to do with breakdown of the Born-Oppenheimer approximation? In molecular spectroscopy you occasionally hear this term thro... -
If you look on the arXiv and in Nature journals there is a continuing stream of people claiming to observe superconductivity in some new mat...
-
I welcome discussion on this point. I don't think it is as sensitive or as important a topic as the author order on papers. With rega...
Hello Prof. McKenzie, this is a student appreciating the single-parameter wonder of the Drude model! What also struck me as being interesting is that Drude took the kinetic model and applied it almost directly to the electron gas case and then merely surmised that the 'scattering time' was electron scattering; according to Ashcroft and Mermin, he had not devised his model with the particular intent of modelling electron-ion collisions. I wonder what would have emerged had he done this...?
ReplyDeleteThere is also the plasma frequency. I'd say it is a two parameter model.
ReplyDeleteJosh,
ReplyDeleteThe beauty of the model is that one does not need to know the physical origin of the scattering.
Peter,
In Drude's version the plasma frequency is given by the density. For elemental metals I do not take to be a free parameter, being determined by the atomic density.
I agree that in the "Drude" model that pops out of the Bloch-Boltzmann model that the plasma frequency is an additional parameter. It is determined by the band structure rather than the electron density.