Quantum Interferences in Superconducting and Normal Metal Arrays

Quantum interferences effects occur in multiconnected metallic structures as result of the coherence of the electronic wave functions. These phenomena are now well understood in superconducting or normal metal periodic networks. We present results of magnetoresistance measurements in normal metal arrays (Mg, Au, Cu) of typical lattice spacing 3 μm. Oscillations of the magnetoresistance with period Φ 0 = hc /2 e (magnetic flux per unit cell) are observed as expected in the weak localization (W.L.) regime. Quantitative comparison with the W.L. theory, recently extended to the network geometry, provides an accurate determination of the characteristic scattering parameters. In superconducting networks, more dramatic interference effects are observed. In addition to the Φ 0 periodicity (flux quantization in elementary loops) fine structures are observed in the critical temperature T c at fractional values p Φ 0 / q . The physical origin of these effects will be discussed. On the other hand, new results on the a.c. susceptibility and magnetization of a superconducting network below T c will be reported.