| Chronology | Current Month | Current Thread | Current Date |
| [Year List] [Month List (current year)] | [Date Index] [Thread Index] | [Thread Prev] [Thread Next] | [Date Prev] [Date Next] |
In particular, note that the hole not only has a funny charge (opposite to
the electron), it has a funny mass (less than zero). For a discussion of
effective mass, look near the end of
http://www.chem.utoronto.ca/staff/GAO/flashed/courses_files/CHM238Yset3.pdf
The bubble in Tim's shampoo has negative (dressed) mass. Note that it goes
!up! when subjected to a gravitational field.
Here are some charts that may help drive home the point:
Electron (q<0, m>0):
+ ========> - applied electric field
<=== force
<=== momentum
<=== velocity
===> conventional current
Proton, or ion in solution (q>0, m>0):
+ ========> - applied electric field
===> force
===> momentum
===> velocity
===> conventional current
Hole in a sea of electrons (q>0, m<0)
+ ========> - applied electric field
===> force
<=== momentum
===> velocity
===> conventional current
Note the funny velocity-versus-momentum relationship for the holes. Also
the funny force-makes-momentum relationship. You may be wondering why the
latter doesn't violate Newton's third law, i.e. violate conservation of
momentum. Positive force makes negative momentum?!!! That sounds bad, but
it turns out to be OK. Analogy: This is like asking how a bat can
increase the energy of a batted ball, when in the bat's frame of reference
the collision is (at best) symmetric or (more likely) lossy. That is: You
get into trouble when you mix viewpoints. The applied electric field (and
the resulting force) originates in the undressed viewpoint. When you
transform it to the dressed viewpoint, you get a force on the hole, but you
also get other terms that dump momentum into the crystal and/or the
uninteresting sea. These other terms don't affect the kinematics of the
hole, but they suffice to ensure that real-world momentum is conserved.