Three separate measurements on three different metals are described below
PHYSICS · Multi-part · Fermi University Physics · Condensed Matter, Materials & Soft Matter · Free electrons, energy bands and electronic structure · Electronic transport in solids
Solid State Physics, Ch The Boltzmann equation and electrical transport
Problem
Three separate measurements on three different metals are described below. For each, translate the description into the physical statement asked for.
((a)) A copper bar of uniform cross-section and uniform temperature carries a steady current driven by a constant applied field E. The occupation function g(r,k,t) obeys ∂t∂g+v⋅∇rg+k˙⋅∇kg=(∂t∂g)coll. State which term(s) of this equation vanish for this bar and name the physical process represented by each term that survives.
((b)) Copper's phonon-limited resistivity falls by a factor of 27 between 40K and 20K, and its Bloch-Gruneisen fit gives ΘR=333K. Nickel's phonon-limited resistivity is found to fall by the same factor of 27, but between 80K and 40K. Using the fact that the Bloch-Gruneisen resistivity depends on temperature only through the ratio T/ΘR, estimate nickel's ΘR.
((c)) The transverse magnetoresistance of a cubic metal carrying current along [001] is measured as the field B (held perpendicular to the current) is rotated in the plane transverse to the current. The trace shows sharp, non-saturating rises whenever B points along [100] or [010], with ordinary saturating behaviour at all other orientations. State what this pattern implies about the metal's Fermi surface, and for which field directions it supports open orbits.