25-10-2012, 04:14 PM
ELECTRON SCATTERING and RESISTIVITY OF METALS
We find from the graph shown that as we goes on reducing the temp of a metal then it’s resistivity also decreases & vice versa but assume a constant value of temp. below 6 K.
In general, the resistivity of a perfect, pure single crystal of a metal approaches to zero as temp. T approaches zero. This signifies that at very low temp. the mean free path λ assumes microscopic values .This concludes that the earlier discussions are not individual ion cores.
predicts mean free path λ of a few angstroms. This classical picture breaks down since experimental values of λ have macroscopic values at extremely low temp. The reason for the break down of the classical approach lies in the wave nature of the elementary particles . Considering the wave nature of e- we can prove that “an e- moving in a perfectly periodic lattice would not be scattered at all” . The wave representing a moving e- in a perfect lattice behave in the same general way as the electromagnetic waves in the visible spectrum passing undeviated through a crystal of sodium chloride say .
Summation done in eqn (3) because the scattering probabilities are additive . Let tT represent the relaxation time associated with a given concentration of imperfections , i.e. for a given concentration of impurities & dislocated atoms .
We find from the graph shown that as we goes on reducing the temp of a metal then it’s resistivity also decreases & vice versa but assume a constant value of temp. below 6 K.
In general, the resistivity of a perfect, pure single crystal of a metal approaches to zero as temp. T approaches zero. This signifies that at very low temp. the mean free path λ assumes microscopic values .This concludes that the earlier discussions are not individual ion cores.
predicts mean free path λ of a few angstroms. This classical picture breaks down since experimental values of λ have macroscopic values at extremely low temp. The reason for the break down of the classical approach lies in the wave nature of the elementary particles . Considering the wave nature of e- we can prove that “an e- moving in a perfectly periodic lattice would not be scattered at all” . The wave representing a moving e- in a perfect lattice behave in the same general way as the electromagnetic waves in the visible spectrum passing undeviated through a crystal of sodium chloride say .
Summation done in eqn (3) because the scattering probabilities are additive . Let tT represent the relaxation time associated with a given concentration of imperfections , i.e. for a given concentration of impurities & dislocated atoms .