Authors
IV Bobkova, AM Bobkov, MA Silaev
Abstract
Dynamic states offer extended possibilities to control the properties of quantum matter. Recent efforts are focused on studying the ordered states which appear exclusively under the time-dependent drives. Here, we demonstrate a class of systems with dynamic spin-triplet superconducting order stimulated by the alternating electric field. The effect is based on the interplay of ferromagnetism, interfacial spin-orbital coupling, and the condensate motion driven by the field, which converts hidden static p -wave order produced by the joint action of the ferromagnetism and the spin-orbital coupling into dynamic s-wave equal-spin-triplet correlations. We demonstrate that the critical current of Josephson junctions hosting these states is proportional to the electromagnetic power supplied by external irradiation or the ac current source. Based on these unusual properties, we propose the scheme of a Josephson transistor which can be switched by the ac voltage and demonstrates an even-numbered sequence of Shapiro steps. Combining the photoactive Josephson junctions with recently discovered Josephson phase batteries, we find photomagnetic SQUID devices that can generate spontaneous magnetic fields while exposed to irradiation.
2 comments
PLee
Yet, you seem to mention that in your system equilibrium superconductivity is fragile. Why?
What do you assume the equilibrium state to be? Have you considered driving on top of the odd-frequency state?
mikesilaev
Indeed, robust spin-triplet Cooper pairs can exist in equilibrium.
But to generate them, magnetic inhomogeneity is needed, e.g., see Rev. Mod. Phys. (2005) by Bergeret, Volkov, Efetov
or some interfacial spin-flip scattering, see https://www.nature.com/articles/nphys831 .
Alternatively, one can use interfacial spin-orbit coupling, as suggested by
https://journals.aps.org/prb/abstract/10.1103/PhysRevB.89.134517
However, in configuration with Rashba spin-orbit coupling and the in-plane magnetization, it occurs that no
robust spin-triplet Cooper pairs are produced.
In this case, adding the orbital motion of condensate induced by an electromagnetic field is the only robust spin-triplet Cooper pairs source. This is the key finding of our paper.
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