Non-equilibrium charge and spin transport in superconducting– ferromagnetic– superconducting point contacts
Journal article, 2018

The conventional Josephson effect may be modified by introducing spin-active scattering in the interface layer of the junction. Here, we discuss a Josephson junction consisting of two s-wave superconducting leads coupled over a classical spin that precesses with the Larmor frequency due to an external magnetic field. This magnetically active interface results in a time-dependent boundary condition with different tunnelling amplitudes for spin-up and -down quasi- particles and where the precession produces spin-flip scattering processes. As a result, the Andreev states develop sidebands and a non-equilibrium population that depend on the details of the spin precession. The Andreev states carry a steady-state Josephson charge current and a time-dependent spin current, whose current–phase relations could be used to characterize the precessing spin. The spin current is supported by spin-triplet correlations induced by the spin precession and creates a feedback effect on the classical spin in the form of a torque that shifts the precession frequency. By applying a bias voltage, the Josephson frequency adds another complexity to the situation and may create resonances together with the Larmor frequency. These Shapiro resonances manifest as torques and, under suitable 2conditions, are able to reverse the direction of the classical spin in sub-nanosecond time. Another characteristic feature is the subharmonic gap structure in the DC charge current displaying an even–odd effect attributable to precession-assisted multiple Andreev reflections. 
This article is part of the theme issue ‘Andreev bound states’.

superconductivity

magnetism

Andreev bound states

Shapiro steps

Landau–Lifshitz–Gilbert equation

multiple Andreev reflection

Author

Cecilia Holmqvist

Wolfgang Belzig

Mikael Fogelström

Chalmers, Microtechnology and Nanoscience (MC2)

Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences

1364-503X (ISSN) 1471-2962 (eISSN)

Vol. 376 20150229

Små okonventionella supraledare gryn och supraledande kontakter

Swedish Research Council (VR), 2016-01-01 -- 2019-12-31.

Competing order in strongly correlated superconductors and in unconventional hybrid junctions

Swedish Research Council (VR), 2013-01-01 -- 2015-12-31.

Areas of Advance

Nanoscience and Nanotechnology

Roots

Basic sciences

Infrastructure

C3SE (Chalmers Centre for Computational Science and Engineering)

Subject Categories

Nano Technology

Condensed Matter Physics

DOI

10.1098/rsta.2015.0229

More information

Created

6/26/2018