RELAXATION OF THE CYCLOTRON SPIN-FLIP EXCITATION IN A SPIN-UNPOLARIZED QUANTUM HALL SYSTEM
S. Dickmann
Institute for Solid State Physics of RAS, 142432 Chernogolovka, Moscow District, Russia
E-mail: dickmann@mail.ru

Received 20 April 2012; accepted 7 June 2012

Cyclotron spin-flip excitation in an even-integer quantum Hall system is the lowest-energy excitation separated from the ground state by the gap slightly smaller than the cyclotron energy, and from the upper magnetoplasma excitation by the Coulomb gap [1, 2]. At the filling factor ν = 2 in a real system these gaps are in the vicinity of 10 meV and 0.5 meV and thus are much larger than the Zeeman gap (~ 0.1 meV) and temperature (< 0.01 meV) respectively. Under these conditions the cyclotron spin flip excitation can not relax in a purely electronic way but only with emission of a short-wave phonon (k ~ 3·10⁷/cm). As a result the relaxation in a modern wide-thickness quantum well occurs very slowly, the characteristic relaxation time being ~ 1 s. The cyclotron spin-flip excitation in the narrow vicinity of filling factors ν = 2, 4, ... should therefore be considered as a collective metastable excitation in the quantum Hall system.