Giant triplet proximity effect in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>π</mml:mi></mml:math>-biased Josephson junctions with spin-orbit coupling

Abstract

In diffusive Josephson junctions the phase difference $\ensuremath{\phi}$ between the superconductors strongly influences the spectroscopic features of the layer separating them. The observation of a uniform minigap and its phase modulation were only recently experimentally reported, demonstrating agreement with theoretical predictions up to now---a vanishing minigap at $\ensuremath{\phi}=\ensuremath{\pi}$. Remarkably, we find that in the presence of intrinsic spin-orbit coupling a giant proximity effect due to spin-triplet Cooper pairs can develop at $\ensuremath{\phi}=\ensuremath{\pi}$, in complete contrast to the suppressed proximity effect without spin-orbit coupling. We here report a combined numerical and analytical study of this effect, proving its presence solely based on symmetry arguments, which makes it independent of the specific parameters used in experiments. We show that the spectroscopic signature of the triplets is present throughout the entire ferromagnetic layer. Our finding offers a way to artificially create, control, and isolate spin-triplet superconductivity.