From the BBC report Plan for quake 'warning system', a quite-confusing paragraph: According to their theory, the charge carriers consist of a specific type of electron, called a phole, which can travel large distances in laboratory experiments..

Now, anyone who knows what an electron is will be confused by that. How can it be special? An electron is a subatomic particle, and those are (from memory) distinguished by charge, spin and mass. The only thing that can possibly distinguish one electron from another is its time-space vector: i.e. where it is, and how fast it's moving in what direction.

(It turns out that a phole is not a specific type of electron. In fact, it's the exact opposite of any type of electron, in that it's the complete absence of an electron where one ought to be. In semi-conductor physics, it's a positive charge carrier, as in P-type semiconductors.)