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Since a number of years, the field of superconductivity has a growing obsession with Majorana fermions. I wonder how far back we can go: When was the first time that superconducting quasiparticles were called Majorana fermions? I am interested specifically in the term "Majorana fermion", rather than the concept of a particle that is its own antiparticle. One can argue that any quasiparticle excitation (socalled Bogoliubov quasiparticle) in a superconductor is a Majorana fermion [*], and then this concept would go back half a century to Bogoliubov. But when was the name of Ettore Majorana first linked to superconducting quasiparticles?

The first appearance I know of is 17 June 1999, when Senthil and Fisher posted their article on Quasiparticle localization in superconductors with spin-orbit scattering.

Is there an earlier source?


[*] An easy way to understand that Bogoliubov quasiparticles are Majorana fermions, is to note that the Bogoliubov-De Gennes equation can be transformed into a real wave equation upon a unitary transformation. It is then analogous to the real Majorana equation, with the superconducting order parameter playing the role of the Majorana mass. The pairwise annihilation of Majorana fermions, searched for in double-beta-decay of neutrinos, also has an analogue for Bogoliubov quasiparticles, as explained here.


Update (January 2016): professor Charles Marcus has pointed me to a 1993 paper on Odd frequency pairing in the Kondo lattice that represents superconducting quasiparticles by Majorana fermions, following up on earlier work on the Kondo problem. A difference with the 1999 papers cited above, is that for the Kondo problem the Majorana representation is used to encode the spin degree of freedom, rather than the electron-hole degree of freedom.

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    $\begingroup$ Could you post a self question-answer explaining how a normal superconducting quasiparticle can be viewed as a Majorana Fermion? $\endgroup$ – DanielSank Apr 10 '15 at 15:18
  • $\begingroup$ @DanielSank --- I added a note with a reference to explain this correspondence. $\endgroup$ – Carlo Beenakker Apr 10 '15 at 15:55
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    $\begingroup$ This might be more suited at History of Science and Mathematics, since it doesn't actually ask any question about the physics content. $\endgroup$ – ACuriousMind Apr 10 '15 at 16:46
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    $\begingroup$ please don't transfer to HSM --- this is really a reference request rather than a "historical" question. $\endgroup$ – Carlo Beenakker Apr 10 '15 at 17:50
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The below seems to be a candidate for the first use of the term 'Majorana fermion'. (I'm not sure if it satisfies your other criteria.)

Salam, Abdus, and J. Strathdee. Super-symmetry and non-Abelian gauges. International Centre for Theoretical Physics, Trieste (Italy), 1974.

enter image description here

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    $\begingroup$ thanks, this might answer the question "who coined the term Majorana fermion". That's an interesting question, which I would also like to know the answer to, although my primary motivation is to know when this term was first applied to superconducting quasiparticles (rather than elementary particles). $\endgroup$ – Carlo Beenakker Apr 12 '15 at 7:23

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