Periodic negative magnetoresistance in granular YBa ₂ Cu ₃ O _{7− δ} nanowires

Abstract

Magneto-transport measurements in YBa2Cu3O7−δ nanowires, comprising a single layer of a small number of grains, reveal periodic magnetoresistance oscillations in a wide temperature range below the transition. The rich structure of these oscillations manifests a negative magnetoresistance in the initial part of each cycle beginning at zero magnetic field. The salient features of these unique oscillations indicate the presence of π Josephson junctions in the granular wires, arising from the d-wave pairing symmetry in YBa2Cu3O7−δ.