Driving the field-free Josephson diode effect using Kagome Mott insulator barriers

Michiel P. Dubbelman; Heng Wu; Joost Aretz; Yaojia Wang; Chris M. Pasco; Yuzhou Zhao; Trent M. Kyrk; Jihui Yang; Xiaodong Xu; Tyrel M. McQueen; Malte Roesner; Mazhar N. Ali

arXiv · 2512.17099

Driving the field-free Josephson diode effect using Kagome Mott insulator barriers

Michiel P. Dubbelman·Heng Wu·Joost Aretz·Yaojia Wang·Chris M. Pasco·Yuzhou Zhao·Trent M. Kyrk·Jihui Yang·Xiaodong Xu·Tyrel M. McQueen·Malte Roesner·Mazhar N. Ali

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Abstract

Josephson junctions (JJs), devices consisting of two superconductors separated by a barrier, are of great technological importance, being a cornerstone of quantum information processing. Classical understanding of superconductor-insulator-superconductor JJs is that conventional insulator's properties, other than magnetism, do not significantly influence the junction's behavior. However, recent work on quantum material (QM) JJs - using Mott insulator Nb3Br8 - resulted in magnetic field-free non-reciprocal superconductivity, termed the Josephson diode effect (JDE), implying the QM's intrinsic properties can modulate superconductivity in non-trivial ways. To date, the underlying mechanism and dependence of the JDE on correlation strength (U/t) has not been elucidated. Here we fabricate QMJJs using correlated Kagome insulators with varying U/t, Nb3X8 (X=Cl, Br, I), observing a decreasing trend of the field-free JDE with Nb3Cl8 reaching ~48% efficiency, Nb3Br8 ~6%, and Nb3I8 having no discernible JDE, matching the trend of decreasing U/t from Cl to I and suggesting correlation in insulators drives the field-free JDE.

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Michiel P. Dubbelman, Heng Wu, Joost Aretz, Yaojia Wang, Chris M. Pasco, Yuzhou Zhao, Trent M. Kyrk, Jihui Yang, Xiaodong Xu, Tyrel M. McQueen, Malte Roesner, Mazhar N. Ali. 2025-12-18. Driving the field-free Josephson diode effect using Kagome Mott insulator barriers. https://arxiv.org/abs/2512.17099

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