On 16 Aug 2003 10:16:17 -0400, "LIJO"
wrote:

Hi
I have a doubt
It is said that the effective mass of holes are greater than that of
electrons .. A hole is a said to be a " lack of electon "....therefore a
hole is not a particle ..Then how come a hole have higher effetive mass than
an electron

thanks
John





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Well, saying a hole is like a missing electron is only an analogy.
Both holes and electrons in a crystal are not really particles in the
ordinary sense at all, but disturbances in the sea of electrons. The
periodic potential of the atoms changes everything. as an example, in
free space an electron follows newton's law, ACCELERATION = force /
mass, with a force being charge times electric field (a = qE/m). In
a crystal, an electron follows the law that VELOCITY = field *
mobility (v = E mu). The mass changes from moment to moment according
to the instantaneous energy and momentum of the particle. Both
"particles" are really just solutions to the Schrodinger equation in a
periodic potential. The mass is defined by analogy with a classical
particle as inversely proportional to the second derivative of energy
with respect to momentum. However this is really just a definition as
it doesn't satisfy any of the usual meanings of mass - it doesn't
correspond to the gravitational attraction on an electron (whatever
that would mean in the context of a crystal) and it doesn't correspond
to the intertial mass (since the F=ma equation doesn't even hold), and
it's not conserved. In the light of all that, why a hole or electron
should have similar masses, or even have masses anywhere near a
regular electron is kind of moot. Indeed, in some crystals, the
"mass" is 100 times smaller than the free electron mass.




Dick Locke wrote in message . ..
On 16 Aug 2003 10:16:17 -0400, "LIJO"
wrote:

Hi
I have a doubt
It is said that the effective mass of holes are greater than that of
electrons .. A hole is a said to be a " lack of electon "....therefore a
hole is not a particle ..Then how come a hole have higher effetive mass than
an electron

thanks
John





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