Influence of Small-Angle Diffraction on the Ballistic Conductance Fluctuations in Chaotic Billiards

Abstract

The ballistic conductance fluctuations (CF) in chaotic billiards are studied using an extended semiclassical approximation. We show that the effect of small-angle diffraction (SAD) on classical electron paths is essential for describing the ballistic CF. By incorporating the SAD effect, we find that both the diffuson and cooperon processes equally contribute to the variance of the transmission coefficient T, in contrast to the result by Jalabert et al. [Phys. Rev. Lett. 65 (1990) 2442] in which only the diffuson process appears. Our result indicates that, in the presence of a magnetic field, the variance of T decreases precisely by a factor of two due to the sensitive suppression of the cooperon contribution. We also determine the full magnetic-field correlation function of T.