标题： Ising超导体/反铁磁Josephson结中的无磁场Josephson二极管效应 显示英文标题

标题： Field free Josephson diode effect in Ising Superconductor/Altermagnet Josephson junction

摘要： 反铁磁超导体（AMs）是一类奇异的反铁磁材料，在没有净全局磁化和自旋轨道耦合（SOC）效应的情况下也表现出自旋分裂现象。 在这项工作中，我们理论研究了Ising超导体/反铁磁体/Ising超导体（ISC/AM/ISC）约瑟夫森结中的超电流非互易性，揭示了不对称的约瑟夫森临界电流、$0 - \pi$转变以及异常的电流-相位关系（CPR）。即使在没有SOC的情况下，在常规超导体（SC）中，由于AM强度和取向的综合作用，观察到了强约瑟夫森二极管效率（JDE）。然而，在存在内禀SOC（ISOC）的情况下，这种效率显著增强，在基于单带和双带ISC/AM的约瑟夫森结中都表现出了明显的二极管效应。此外，观察到在所有情况下，对于更高的AM强度和中间取向，JDE更为显著。值得注意的是，对于取向$0^\circ$和$45^\circ$，它被显著抑制。我们的结果还表明，势垒透明度和AM长度在优化JDE方面起着关键作用。在单带ISC/AM系统中，无论AM长度如何，JDE都会持续存在；而在双带ISC/AM系统中，当AM结较长时，JDE会减弱。此外，我们的结果表明，通过考虑较强的AM强度，在单带和双带ISC/AM约瑟夫森结中都可以实现高达$\sim 52\%$的二极管效率。此外，与双带ISC相比，单带ISC提供了更广泛的AM取向范围，以实现更好的调谐和JDE优化。我们的发现强调了AM强度、取向和ISOC对JDE效率的影响，为超导二极管设计提供了见解。 显示英文摘要

摘要： Altermagnets (AMs) are an exotic class of antiferromagnet that exhibit spin-splitting even at the absence of net global magnetization and spin-orbit coupling (SOC) effects. In this work, we investigated theoretically, the supercurrent nonreciprocity in an Ising Superconductor/Altermagnet/Ising Superconductor (ISC/AM/ISC) Josephson junction which revealed asymmetric Josephson critical currents, $0 - \pi$ transitions and anomalous current-phase relationship (CPR). A strong Josephson diode efficiency (JDE) is observed due to the combined effects of AM strength and orientations in a conventional SC even in absence of SOC. However, it significantly enhances in presence of intrinsic SOC (ISOC), resulting in pronounced diode effect in both single and double band ISC/AM based Josephson junction. Additionally, it is observed that JDE is more prominent at higher AM strengths with intermediate orientations in all scenario. Notably, it is significantly suppressed for orientations $0^\circ$ and $45^\circ$. Our results also indicate that barrier transparency and AM lengths play a crucial role in optimizing the JDE. In a single-band ISC/AM system JDE persists for any AM length, while reduces at longer AM junction in case of a double-band ISC/AM system. Moreover, our results suggest that a diode efficiency of $\sim 52\%$ can be achieved in the proposed Josephson junction in both single and double band ISC/AM Josephson junction by considering strong AM strength. Furthermore, single band ISC offers wide AM orientation range in contrast to double band ISC for better tunability and optimization of JDE. Our findings highlight the impact of AM strength, orientation and ISOC on the JDE efficiency offering insights for superconducting diode design.