Unformatted text preview: 4 gauss? How is the area of the orbit in real space related to the kspace orbit? (20) 4. Consider the problem of an extremal cyclotron orbit in the k x k y plane of the Fermi surface for a nonisotropic solid. The equation for the Fermi energy is E = (Ak k 2 + Bk y 2 ) . Apply a magnetic field along z and describe the rate at which r k changes during an orbit when A and B are unequal. Describe the orbit performed in real space for this situation. (20) 5. (a) What are Friedel oscillations? (b) Show that the induced charge density arising from an impurity in a metal is proportional to r3 cos (2K F r) at large r (calculate). (c) What is the Friedel sum rule? Derive it. (d) Discuss the Kohn effect from the point of view of screening; that is, discuss the influence of the behavior of the Lindhard dielectric function at q = 2k F on the phonon spectrum of a metal....
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 Spring '08
 Cohen
 Electron, Energy, Fundamental physics concepts, Condensed matter physics, Fermi, Fermi surface, extremal cyclotron orbit

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