How to Calculate Mu* for Superconducting Systems Using McMillan Formula?

In summary, the desperate physicist is trying to figure out the critical temperature for a superconducting system. He only has three given quantities- the debye temperature, the electron-phonon coupling constant, and the density of states. He is not sure if the equation he found is correct or not, but he is hoping someone can help him. He has tried different equations but they all seem to be complicated. He is grateful for any help that can be given.
  • #1
angel 42
25
0
Hello everyone, Do you know any equation can help me to calculate the Coulomb pseudo-potential mu*, cause I'm working on McMillan formula
Tc= thetaD/1.45 {-1.04(1+lamda)/[ lamda – mu*(1+ 0.62 lamda)]}

trying to find the critical temperature Tc for a superconducting system I only have three given quantities:
thetaD= 750 K (debye temp)
Lamda= 1.04 (the electron-phonon coupling constant)
N(Ef)= 18.26 state/atom.eV (density of states DOS)
I'm not still sure of this If it's correct or not cause I found many other formulas with different details. offcourse I get this formula from the net, I first choose mu*= 0.1 as most solutions but the prophesier said it's wrong to choose it arbitrarily I have to calculate mu* using the density of state. so I searched the net to find an equation that relates mu* to DOS I found one, but it was very complicated with another unknown quantities like the volume (volume of what, how can I find it from the given numbers and as far as I know the volume of the lattice- assume- couldn't be calculated from them:confused:) It's like self learning of something completely new and never taught before -mybe that's why I couldn't find a way to figure that out. I tried for a week before typing this. I really need to do this please help If anyone can, I appreciate all the help I'll have.

Desperate physicist
:frown:
 
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  • #2
You might want to check out "Principles of Electron Tunneling Spectroscopy " by E L Wolf
 
  • #3
I'm sorry it took a while to respond to this. Most of my text (and my journal access) are either at work, or from work, so most of the stuff I needed to refer to to answer this weren't available to me till today (since I am now at work).

The reference to Wolf's tunneling text isn't as useful because he simply stated it (pg. 523) and then gave you a reference to McMillan's paper (unless I missed it elsewhere in the text).

What you need is the original McMillan's paper (Phy. Rev. 167, 331 (1968)). Look at Eq. 13 of that paper, which was derived in another paper by Morel and Anderson (reference given therein). This is where you need to use the info that you have on the DOS.

Zz.
 
  • #4
I'll see thanks.
 

1. What is the significance of Tc in superconducting systems?

Tc, or critical temperature, is the temperature at which a material transitions from a normal conducting state to a superconducting state. This is an important property in superconducting systems as it determines the maximum temperature at which the material can exhibit zero electrical resistance and perfect diamagnetism.

2. How is Tc affected by external factors?

Tc is affected by various external factors such as magnetic fields, pressure, and impurities in the material. These factors can either increase or decrease the critical temperature, depending on the material and its composition.

3. What is the highest Tc ever achieved in a superconducting system?

The current record for the highest Tc in a superconducting system is held by a material called H3S, which has a critical temperature of 203 K (-70 °C). This was achieved under extremely high pressures of about 155 gigapascals.

4. How does Tc vary among different superconducting materials?

Tc can vary greatly among different superconducting materials, ranging from a few kelvins to over 200 K. This is due to the different physical and chemical properties of the materials, as well as the methods used to synthesize them.

5. Is Tc a fixed value for a specific material?

No, Tc is not a fixed value for a specific material. It can vary depending on external factors, as well as the method of preparation and the quality of the material. Researchers are constantly working to improve Tc in superconducting systems through material design and optimization techniques.

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