Decoherence in Aharonov-Bohm rings

We study electron decoherence by measuring the temperature dependence of Aharonov-Bohm (AB) magnetoconductance oscillations in quasi-1D rings, etched in a high-mobility GaAs/GaAlAs heterostructure. The oscillation amplitude, which is quantified by Fast Fourier Transform (FFT) amplitudes, is influenced both by phase-breaking and by thermal averaging. FFT components of frequency up to six times the fundamental h/e component are observed and used in the analysis. It is crucial to study not only the h/e AB amplitude, but also the higher h/ne components, in order to distinguish the effects of phase-breaking and thermal averaging. For the phase-breaking, it is demonstrated that the damping of the oscillation amplitude is proportional to the length of the interfering paths. For temperatures T from 0.3 to 4 K we find the phase coherence length L_φ ∝ T^-1. The phase coherence length does also seem to depend on sample geometry. Recently, the T^-1 dependence has been predicted theoretically for AB rings by Seelig and Büttiker (Phys. Rev. B 64 (2001) 245313).