The BCS is based on the concept of Cooper pairs (or pairons), which was actually conceived before the BCS. The concept of pairons is widely known and accepted even from researchers who think the BCS is not adequate to describe all types of superconductors. In the BCS, pairons are though to form from singlet electron pairs (with single state and total spin=0) whose total momentum is zero (-k, +k). Is there any cause that prevent triplet spin electrons (with 3 states and total spin=1) to form pairons or even other combinations of multi-pairons in superconductors?
Just to note: the three triplet states have individual spins of -1, 0, +1. Therefore, triplet pairs of electrons also have a state of 0.
From a theoretical point of view Prof. Muhammad Hamza El-Saba, spin-triplet bound states are possible in superfluid systems at very low temperatures (no more than a few K).
You can take for example the A phase of 3He isotope where experiments confirm the existence of such bound states. What is difficult to predict is if the attraction is mediated by phonons or other quasiparticles.
Of course, there will be some symmetry & other properties that have to be followed such as a certain spatial parity, or the strength of spin-orbit interaction of the bound state, and where always an orbital pair momentum L higher than 0 will play the main role.
In addition, those triplet states are seen in experiments when they are split due to an external field (for example in specific heat C measurements under external H in 3He and UPt3, in velocity changes under an external elastic field in Sr2Ru04).
Please see the first 4 short chapters of the following book for a quick and formal summary:
V. Mineev and K. Samokhin. 1999, Introduction to Unconventional Superconductivity. Gordon and Breach Science Publishers.
Best Regards.
You are most welcome, Prof. Muhammad Hamza El-Saba
I can recommend the following classical paper, it points out the differences with respect to singlet pairs:
Superconductivity of an Electron System with Singlet or Triplet Pairs by S. Vonsovskii & M. Svirskii JETP, 1964, Vol. 19, No. 5, p. 1095
http://www.jetp.ac.ru/cgi-bin/e/index/e/19/5/p1095?a=list
Dear Prof. Muhammad Hamza El-Saba
We just published a preprint on triplet paired superconductors, I would like to point out that this result was obtained seven years later. I started to do the calculation in 2014...
Preprint Non-magnetic tight binding disorder effects in the γ sheet of Sr2RuO4
very hard to find the resonance... very hard...
Best Regards...
Thank you Prof. Contreras for your interesting article in this concern I'll read it and come back to you.
Prof. Muhammad Hamza El-Saba
I can now partially answer your question following our last preprint:
Preprint Dressed behavior of the quasiparticles lifetime in the unita...
1. States with only parions (we called them supercarriers) can be formed in triplet models (numerically in the Miyake Narikiyo triplet tiny gap model) only by adding small amounts of non-magnetic dirt.
2. Otherwise, there will be a mix of parions and normal state-dressed quasiparticles for the majority of disorder values, which are responsible for the unique resonance at zero frequency that we call unitary limit.
Please, I attach the slide from which we came to that conclusion.
The effect was observed experimentaly in the following publication a few months ago. They do not know why...
Article Reduced Hall carrier density in the overdoped strange metal ...
Let add another cause that does not allow triplet pairing in unconventional superconductors, Prof. Muhammad Hamza El-Saba
- 1 D irreducible representations for the symmetry point crystal group (Profs. E. Wigner & H. Weyl were responsible for introducing group theory into physics) do not allow triplet pairing.
- 2 D irreducible representations of the point symmetry group of the crystal allow triplet pairing.
I get that conclusion by comparing, the calculation of the elastic cross-section on both cases.
The previous preprint I pointed out was finally published. Some more are coming...
Deleted research item The research item mentioned here has been deleted
Best Regards.
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