# Effective Mass in Metals

1. Nov 15, 2006

### Reality_Patrol

Does anyone have a link or reference to a table on the effective mass of electrons in the common metals?

thanks

2. Nov 16, 2006

### ZapperZ

Staff Emeritus
Obviously, there are smart people here who know better than to tackle this one.

The term "effective mass", even within solid state physics, can in fact have a number of values depending on how it is measured. The "electronic" effective mass can often be derived from band structure dispersion, or measured from the cyclotron resonance, or even obtained from specific heat measurements. All of these need not produce the identical values.

For a table of specific heat effective mass for metals, refer to the table given in Ashcroft and Mermin's Solid State Physics text (1st Ed.) pg. 47. The ratio m*/m (where m is the bare mass) ranges from 0.38 for Sb to 12 for Nb.

Zz.

3. Nov 17, 2006

### Reality_Patrol

Zz,

Thanks for the info. I've got the reference on order. I would like to have some idea of the variation in values given by the different methods of measurement as well. I'm not sure which would be the best value to use given the experiments I'm contemplating. The value will determine many parameters so if the variation is large, the experiment will have to be redone many times.

On a related note, any suggestions on how to go about determining what the contact potential between 2 metals should be?

Thanks again, RP

4. Nov 18, 2006

### ZapperZ

Staff Emeritus
It depends on what the experiemnt is. If you are measuring something related to electronic transport, then the effective mass would be something you use from the band structure calculation or the cyclotron measurement. If you are doing a heat transport experiment, then the specific heat effective mass is the one to use.

I don't know much about that. Maybe someone else has that info. If not, I'll do some checking when I go back to work on Monday.

Zz.

5. Nov 18, 2006

### Gokul43201

Staff Emeritus
There's a standard technique for this - it's called a CPD (contact potential difference) measurement.

I just googled CPD "Kelvin probe" and found this:

http://www.mcallister.com/kpfaqpg.html

6. Nov 18, 2006

### Dr Transport

the electronic effective mass is anisotropic, try looking for Madarasz in Applied Physics back in 83 or 84, he did a calculation in silicon to show the differences in effective mass, density of states effective mass etc.... Depending on the measurement or calculation, you'll need to do different things to get everything you need to be able to accurately extract the correct value from your experiments.