Orientation-dependent exceptional points in non-Hermitian altermagnetic Josephson junctions

Le résumé fourni par la source

Motivated by the orientation-dependent spin splitting and vanishing net magnetization of altermagnets, we study d -wave altermagnetic Josephson junctions (JJs) with a focus on the emergence and controllability of non-Hermitian degeneracies [or exceptional points (EPs)] where both eigenvalues and eigenvectors coalesce. Unlike conventional JJs, the altermagnetic order induces spin- and orientation-dependent Andreev bound states, offering additional control of the Josephson effect. We show that the position of EPs as a function of the superconducting phase difference ϕ can be tuned by the crystal orientation, strength of the altermagnetic order, Rashba spin-orbit coupling, and the degree of non-Hermiticity. Furthermore, the number of EPs is found to be directly tunable by altermagnetic properties. The total supercurrent associated with different transverse momentum k y shows a smooth behavior but sensitive to the crystal orientation and other properties of the altermagnetic JJ. These findings demonstrate a pathway to realizing distinctive non-Hermitian phenomena arising from the interplay among non-Hermiticity, Rashba interaction, superconductivity, and altermagnetism.

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