Orientation-dependent transport in junctions formed by d-wave altermagnets and d-wave superconductors

Abstract

We investigate de Gennes-Saint-James states and Josephson effect in hybrid junctions based on d-wave altermagnet and d-wave superconductor. Even though these states are associated to long junctions, we find that the dx2−y2 altermagnet in a normal metal/altermagnet/d-wave superconductor junction forms de Gennes-Saint-James states in a short junction due to an enhanced mismatch between electron and hole wave vectors. As a result, the zero-bias conductance peak vanishes and pronounced resonance spikes emerge in the subgap conductance spectra. By contrast, the dxy altermagnet only features de Gennes-Saint-James states in the long junction. Moreover, the well-known features such as V-shape conductance for dx2−y2 pairings and zero-biased conductance peak for dxy pairings are not affected by the strength of dxy altermagnetism in the short junction. We also study the Josephson current-phase relation I(φ) of d-wave superconductor/altermagnet/d-wave superconductor hybrids, where φ is the macroscopic phase difference between two d-wave superconductors. In symmetric junctions, we obtain anomalous current phase relation such as a 0−π transition by changing either the orientation or the magnitude of the altermagnetic order parameter and dominant higher Josephson harmonics. Interestingly, we find the first-order Josephson coupling in an asymmetric dx2−y2−superconductor/altermagnet/dxy-superconductor junction when the symmetry of altermagnetic order parameter is neither dx2−y2 nor dxy wave. We present the symmetry analysis and conclude that the anomalous orientation-dependent current-phase relations are ascribed to the peculiar feature of the altermagnetic spin-splitting field.

Source-reported materials — not catalogue approval

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