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.
