Second Harmonic Generation in Submicron GaAs-AlGaAs Wires and Rings.

Second harmonic generation has been observed in submicron wires fabricated in GaAs-AlGaAs heterostructures. The length and width of the wires are less than the elastic and inelastic mean free paths, while the width is comparable to the Fermi wavelength. In contrast to measurements on diffusive metal wires, the voltage response at the n-th harmonic V(nf) to a small current excitation I(f) obeys V(nf) alpha I sup n (f). In concurrence with the Larkin-Khmelnitskii model, we propose that the source of the nonlinearity is quantum interference.