Allen-Dynes Tc and anisotropic Superconducting gap Tc are different

[simba2828]

Dear all,

Could anyone please tell me why my Allen-Dynes Tc and anisotropic Superconducting gap Tc are different?

My input files can be found in my previous question, of which also I am looking for the answer.
viewtopic.php?f=6&t=1761

Allen-Dynes Tc:

Code: Select all

Finish reading a2f file

     Electron-phonon coupling strength =    1.8074196

     Estimated Allen-Dynes Tc =    19.995505 K for muc =    0.10000

     Estimated w_log in Allen-Dynes Tc =    12.891461 meV

     Estimated BCS superconducting gap =     3.032620 meV

     Estimated Tc from machine learning model =    25.660110 K


     WARNING WARNING WARNING

     The code may crash since tempsmin =   30.000 K is larger than Allen-Dynes Tc =    19.996 K

     temp(  1) =     30.00000 K

Anisotropic SC gap profile (for muc = 0.10000) which gives Tc around more than 30K while Allen Dynes Tc is 19.995505 K:

Could anyone please suggest me why this is the case?

[hpaudya1]

Hi Simba2828,

If a material has a highly anisotropic superconducting gap, it is anticipated that its AD Tc (critical temperature for the isotropic component of the gap) will be lower than its anisotropic Tc. For instance, MgB2 serves as an example where you can refer to the literature and observe that the AD Tc is approximately 19 K, while the anisotropic Tc is around 40 K.

Happy EPWing,
Hari

[simba2828]

Thank you Hari Sir for the theoretical insight.
One more question has been raised in my head, maybe I'm being naive and not aware of the proper theory, that if the system having highly anisotropic SC gap then it should show a multi-gap character? Is there any condition like this?

Shubham

[hpaudya1]

Hi Shubham,

I case of MgB2, system is anisotropic and has two gaps from \Sigma and \Pi bands, but we can not always say that the anisotropic SC gap shows a multi-gap character, I think.

Happy EPWing,
Hari

[simba2828]

Thank You Hari Sir for clarifying the query.

Shubham,
IIT Kharagpur, India