Linked Questions

30 votes
2 answers
10k views

Basic questions in Majorana fermions

Why any fermion can be written as a combination of two Majorana fermions? Is there any physical meaning in it? Why Majorana fermion can be used for topological quantum computation?
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  • 2,319
20 votes
4 answers
12k views

What makes a superconductor topological?

I have read a fair bit about topological insulators and proximity induced Majorana bound states when placing a superconductor in proximity to a topological insulator. I've also read a bit about ...
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18 votes
3 answers
5k views

Mean field equations in the BCS theory of superconductivity

In BCS theory, one takes the model Hamiltonian $$ \sum_{k\sigma} (E_k-\mu)c_{k\sigma}^\dagger c_{k\sigma} +\sum_{kk'}V_{kk'}c_{k\uparrow}^\dagger c_{-k\downarrow}^\dagger c_{-k'\downarrow} c_{k'\...
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9 votes
2 answers
2k views

What is a d + id superconductor and why does it break time reversal symmetry?

There are a lot of publications dealing with d-wave and d + id superconductivity, but I found no satisfying answer what exactly makes a superconductor d + id and why they break time reversal symmetry. ...
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4 votes
1 answer
1k views

Literature Request: Introduction to d-wave superconductivity

I'm looking for a pedagogic introduction to d-wave superconductivity. Ideally, this would involve a derivation of d-wave superconductivity and the form of the gap parameter from some fundamental ...
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  • 1,117
6 votes
2 answers
588 views

Do spin-polarised Cooper Pairs break the Pauli exclusion Principle?

So far I learned that electrons of a Cooper pair should have opposite spin to account for Pauli's exclusion principle, because their other quantum numbers are the same. Is this understanding correct? ...
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  • 313
9 votes
0 answers
706 views

Physics uses of $SO(8)$ and Spin(8) triality [closed]

Triality is a relationship among three vector spaces. It describes those special features of the Dynkin diagram D4 and the associated Lie group Spin(8), the double cover of 8-dimensional rotation ...
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  • 7,340
2 votes
1 answer
891 views

Is it necessary for Cooper pair of electrons have opposite spin?

In Cooper pair, is there an essential condition on spin of electrons forming pair? Also explain the reason behind it. And what is the charge on them.
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  • 85
2 votes
0 answers
518 views

What is the source of Chirality in Chiral superconductivity?

Chiral super conductors, have a gap function that rotates in cw or ccw direction as wave vector rotates on fermi surface. E.g. $\Delta_{k}=k_{x}\pm ik_{y}$ or $\Delta_{k}\propto exp(il\phi)$ where $\...
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  • 1,203
2 votes
0 answers
247 views

General questions on the superconducting order parameter

Regarding the concept of singlet and triplet superconductor. In the very good answer to the question What is a $p_x + i p_y$ superconductor? Relation to topological superconductors the answerer says ...
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  • 1,280
2 votes
0 answers
106 views

Can cooper pair formation take place between electrons having same spin?

Since they're bosons, can cooper pairs have spin values other than zero like 1? If the electrons had the same spin, can't their spins add up as 1/2+ 1/2?. Thanks in advance.
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1 vote
0 answers
59 views

Shape of the spin part in the superconducting gap

The conventional way of writing down the gap in a superconducting material $\Delta(k) = \langle \hat{c}_\alpha({\bf k}) \hat{c}_\beta({\bf -k}) \rangle$ is $$\Delta(k) = (\Delta_0(k) + {\bf d(k) \...
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