Noiseless scattering states in a chaotic cavity

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Shot noise in a chaotic cavity (Lyapunov exponent λ, level spacing δ, 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, but not to the shot-noise power S. We find that these noiseless transmission channels do not exist for N√kFL, where we expect the random-matrix result S/2eI=1/4. For N√kFL we predict a suppression of the noise ∝ (kFL/N²)ⁿδ/πℏλ. This nonlinear contact dependence of the noise could help to distinguish ballistic chaotic scattering from random impurity scattering in quantum transport.