STOCHASTIC RESONANCE IN AN ELECTRON-SPIN-NUCLEAR-SPIN SYSTEM

We report a realization of stochastic resonance, based on the intrinsi c bistability of the magnetic resonance of conduction electrons in gal lium oxide [E. Aubay and D. Gourier, Phys. Rev. B 47, 15 023 (1993); D . Gerbault and D. Gourier, ibid. 54, 6315 (1996)]. We show that the re sponse to a small periodic magnetic field of the bistable conduction e lectron-spin-resonance signal can be amplified by the addition of an e xternal random magnetic field. This is experimental evidence of stocha stic resonance in the interaction of an electromagnetic field with an ensemble of two-level quantum systems (the Zeeman energy levels of fre e electrons).