High-energy modes of oscillation in a zero-temperature relativistic electron gas in a strong background magnetic field are reported. The modes propagate parallel to the magnetic field and appear both in a longitudinal and in two transverse polarizations. The underlying mechanism is the binding between electrons near the Fermi surface and virtual positrons, which is enhanced by the presence of the filled Fermi distribution, in a Cooper-pair-like phenomenon. The energy of the mode is of the order of the pair energy (over 1.02 MeV), and the mode exists only for wave numbers k above a critical value, such that the mode group velocity exceeds the velocity of an electron on the Fermi surface. Damping of the mode is insignificant at the critical wave number and increases with k to a relatively small maximum value.

• Received 22 October 1991

DOI:https://doi.org/10.1103/PhysRevA.45.5820