Use of Tricrystal Junctions to Probe the Pairing State Symmetry of YBa2Cu3O 7−δ

Abstract

We propose a new method of probing superconducting pairing state symmetry, using tricrystal devices analogous to $s$- $d$ corner junctions. Two central peaks are observed in the field-modulated critical currents of frustrated YB${\mathrm{a}}_2$C${\mathrm{u}}_3$O ${}_{7-\delta }$ tricrystal junctions operating in the short junction limit, consistent with $d_{x^2{-y}^2}$ pairing symmetry, while a single peak is observed for unfrustrated tricrystal devices. A single peak is also observed for frustrated tricrystal junctions operating in the long junction limit, and it is shown theoretically that $s$- and $d$-wave superconductors behave the same in this limit.