Stochastic resonance in monostable systems

The first observations of noise-induced enhancements and phase shifts of a weak periodic signal - characteristic signatures of stochastic resonance (SR) - are reported for a monostabable system. The results arc shown to be in good agreement with a theoretical description based on linear-response theory and the fluctuation dissipation theorem. It is argued that SR is a general phenomenon that can in principle occur for any underdamped nonlinear oscillator