INFLUENCE OF SMALL-ANGLE DIFFRACTION ON THE BALLISTIC CONDUCTANCE FLUCTUATIONS IN CHAOTIC BILLIARDS

The ballistic conductance fluctuation (CF) in chaotic billiards are st udied using an extended approximation. We show that the effect of smal l-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 t he variance of the transmission coefficient T, in contrast to the resu lt by Jalabert et al. [Phys. Rev. Lett. 65 (1990) 2442] in which only the diffuson process appears. Our result indicates that, in the presen ce of a magnetic field. the variance of T decreases precisely by a fac tor of two due to the sensitive suppression of the cooperon contributi on. We also determine the full magnetic-field correlation function of T.