${\phi }_0$-Josephson junction in twisted bilayer graphene induced by a valley-polarized state

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 ${\phi }_0$-junction in which the two superconductors acquire a finite phase difference ${\phi }_0$ in the ground state. We point out that the emergence of the ${\phi }_0$-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 ${\phi }_0$-junctions with applications in superconducting devices.

7 pages, 4 figures, plus Supplementary Material

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Cited by in corpus (14)

• Josephson Diode Effect Induced by Valley Polarization in Twisted Bilayer Graphene
• The supercurrent diode effect and nonreciprocal paraconductivity due to the chiral structure of nanotubes
• Field-Effect Josephson Diode via Asymmetric Spin-Momentum-Locking States
• Gate-Defined Topological Josephson Junctions in Bernal Bilayer Graphene
• Junctions and superconducting symmetry in twisted bilayer graphene
• Proximity-induced equilibrium supercurrent and perfect superconducting diode effect due to band asymmetry
• Intrinsic non-magnetic ${\varphi }_0$ Josephson junctions in twisted bilayer graphene
• Probing the order parameter symmetry of two-dimensional superconductors by twisted Josephson interferometry
• Transverse Cooper-Pair Rectifier
• Anomalous $h/2e$ periodicity and Majorana zero modes in chiral Josephson junctions
• Reducing the frequency of the Higgs mode in a helical superconductor coupled to an LC-circuit
• Valley Gapless Semiconductor: Models and Applications
• Gate-tunable Josephson diodes in magic-angle twisted bilayer graphene
• Current-induced re-entrant superconductivity and extreme nonreciprocal superconducting diode effect in valley-polarized systems