Josephson effect in a multiorbital model for Sr2RuO4

Abstract

We study Josephson currents between s-wave/spin-triplet superconductor junctions by taking into account details of the band structures in Sr2RuO4, such as three conduction bands and spin-orbit interactions in the bulk and at the interface. We assume five superconducting order parameters in Sr2RuO4: a chiral p-wave symmetry and four helical p-wave symmetries. We calculate the current-phase relationship I(φ) in these junctions, where φ is the macroscopic phase difference between the two superconductors. The results for a chiral p-wave pairing symmetry show that a cos(φ) term appears in the current-phase relation because of time-reversal symmetry (TRS) breaking. On the other hand, this cos(φ) term is absent in the helical pairing states that preserve TRS. We also study the dependence of the maximum Josephson current Ic on an external magnetic flux Φ in a corner junction. The calculated Ic(Φ) obeys Ic(Φ)≠Ic(−Φ) in a chiral state and Ic(Φ)=Ic(−Φ) in a helical state. We calculate Ic(Φ) in a corner superconducting quantum interference device (SQUID) and a symmetric SQUID geometry. In the latter geometry, Ic(Φ)=Ic(−Φ) is satisfied for all the pairing states and it is impossible to distinguish a chiral state from a helical one. On the other hand, a corner SQUID always gives Ic(Φ)≠Ic(−Φ) and Ic(Φ)=Ic(−Φ) for a chiral and a helical state, respectively. Experimental tests of these relations in corner junctions and SQUIDs may serve as a tool for unambiguously determining the pairing symmetry in Sr2RuO4.

Source-reported materials — not catalogue approval

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