PHASE–SENSITIVE ANDREEV CONDUCTANCE OF AN SNS SYSTEM WITH THE SUPPRESSED PROXIMITY EFFECT

A study is made of the dissipative component of the electron transport in a doubly connected Andreev SNS interferometer with elastic mean free paths l_el in the metals of around 100μm and a macroscopic phase–breaking length which is two or more orders of magnitude larger than in disordered nanostructures. At helium temperatures, the samples are found to exhibit new phase–sensitive effects of a quantum–interference nature. Below 2K, the conductance of the macroscopic N region of the system has an oscillatory component of resonance shape which undergoes the phase inversion relative to the phase of the nonresonance oscillations. An explanation for the effects is suggested in terms of the contribution to the Josephson current from coherent quasiparticles with energies of order of the Thouless energy. The temperature behavior of the dissipative transport in a pure normal metal near an isolated NS point contact is studied.