$φ_0$-Josephson junction in twisted bilayer graphene induced by a valley-polarized state

Ying-Ming Xie; Dmitri K. Efetov; K. T. Law

doi:10.1103/PhysRevResearch.5.023029

paper

$φ_{0}$ -Josephson junction in twisted bilayer graphene induced by a valley-polarized state

arXiv:2202.05663 · doi:10.1103/PhysRevResearch.5.023029

Abstract

Recently, gate-defined Josephson junctions in magic angle twisted bilayer graphene (MATBG) were studied experimentally and highly unconventional Fraunhofer patterns were observed. In this work, we show that an interaction-driven valley-polarized state connecting two superconducting regions of MATBG would give rise to a long-sought-after purely electric controlled $φ_{0}$ -junction in which the two superconductors acquire a finite phase difference $φ_{0}$ in the ground state. We point out that the emergence of the $φ_{0}$ -junction stems from the valley-polarized state which breaks time-reversal symmetry and trigonal warping effects which break the intravalley inversion symmetry. Importantly, a spatially non-uniform valley polarization order parameter at the junction can explain the highly unconventional Fraunhofer patterns observed in the experiment. Our work explores the novel transport properties of the valley-polarized state and suggests that gate-defined MATBG Josephson junctions could realize the first purely electric controlled $φ_{0}$ -junctions with applications in superconducting devices.

arXiv comment7 pages, 4 figures, plus Supplementary Material

$φ_{0}$ -Josephson junction in twisted bilayer graphene induced by a valley-polarized state

Abstract

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Cited by in corpus (14)

φ0​-Josephson junction in twisted bilayer graphene induced by a valley-polarized state

Abstract

References in corpus (72)

Cited by in corpus (14)

$φ_{0}$ -Josephson junction in twisted bilayer graphene induced by a valley-polarized state