Conductance fluctuations and chaotic scattering in ballistic microstructures

Abstract

We report detailed measurements of the low-temperature magnetoconductance in ballistic microstructures in the shape of a ``chaotic'' stadium and a circle with quantum-point-contact leads. Both structures show large, aperiodic, conductance fluctuations as a function of perpendicular magnetic field, and a zero-field resistance peak indicating geometry-dependent enhanced backscattering. Power spectra of fluctuations are consistent with recent semiclassical analyses based on quantum chaotic scattering, with the circle showing enhanced high-frequency spectral content.