Real-space and magnetic-field correlation of quantum-resistance fluctuations in the ballistic regime in narrow GaAs-${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As wires

We report the first experimental study, in the quasiballistic regime, of magnetic field correlation properties of quantum-resistance fluctuations, between phase coherent spatial regions. Our devices are GaAs-${\mathrm{Al}}_{\mathrm{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As quasi-one-dimensional wires with an elastic-scattering length comparable to the voltage probe spacing and at most 10 transverse channels occupied. We find the correlation coefficients to be substantially different than recent results in diffusive wires (∼0 compared to -0.5 for the latter), indicating that the universality, which characterizes fluctuations in diffusive quantum transport, is beginning to break down in this few-channel, ballistic limit.