What Units Are Used in Solid State Physics Equations?

[zakk87]

I'm having some troubles understanding the unit used in solid state physics. In a paper I read

$$\Lambda a \sim 1$$

where $\Lambda$ is a momentum cutoff and $a$ is the lattice spacing of a crystal. Questions:

1) What kind of units are customarily used in solid state physics scientific articles? Can I be confident that they are atomic units?

2) The aforementioned equation is not correct as far as the units of measure are concerned. If this was solid state physics, I would say that one could set the speed of light and the Planck constant to 1 and make the equation correct. However in a low energy treatment in solid state physics, I don't see the point in using the speed of light or the Planck constant, and making the physics of the system dependent upon these quantities.

Thanks in advance for your answers.

 

[nasu]

I don't know what you mean by "atomic units".
However the momentum of electrons in crystals may be given or plotted in terms of "k", the wave-vector.
The momentum p can be written as $$p=\hbar k$$ where k is the wavevector.
Your capital lambda is probably the maximum value of k along that direction.
It has units of inverse meter.