Noiseless scattering states in a chaotic cavity

Shot noise in a chaotic cavity (Lyapunov exponent lambda, level spacing delta, linear dimension L), coupled by two N-mode point contacts to electron reservoirs, is studied as a measure of the crossover from stochastic quantum transport to deterministic classical transport. The transition proceeds through the formation of fully transmitted or reflected scattering states, which we construct explicitly. The fully transmitted states contribute to the mean current (I) over bar, but not to the shot-noise power S. We find that these noiseless transmission channels do not exist for N less than or similar to rootk(F)L, where we expect the random-matrix result S/2e (I) over bar = 1/4. For N greater than or similar to rootk(F)L we predict a suppression of the noise proportional to(k(F)L/N-2)(Ndelta/pihlambda). This nonlinear contact dependence of the noise could help to distinguish ballistic chaotic scattering from random impurity scattering in quantum transport.