MESOSCOPIC FLUCTUATIONS IN HIGH MAGNETIC FIELDS — ARE THEY STILL UNIVERSAL?

Abstract

Universal conductance fluctuations (UCF) arise in mesoscopic systems as a direct consequence of the quantum interference of electron waves. The universal feature of the fluctuations is that, at finite temperature, their behaviour can be expressed in terms of one parameter, the phase breaking length of electrons Lϕ. Though the mesoscopic fluctuations have also been observed in high magnetic fields, ω c τ > 1, where ω c is the cyclotron frequency and τ the electron scattering time, it was widely believed that the magnetic field had to suppress the fluctuations. However, experiments on an orthodox mesoscopic system have found out no signs of the suppression. The fluctuation amplitude remains unchanged in high magnetic fields while the period of fluctuations changes dramatically. This indicates the breakdown of universal scaling at high magnetic fields.