The superconducting diode effect is nonreciprocal, non-dissipative current flow in a superconducting system: current passes more easily in one direction than the other. The source digest covers it through the theoretical work of Tim Kokkeler, Ilya Tokatl and F. Sebastian Bergeret, "Nonreciprocal superconducting transport and the spin Hall effect in gyrotropic structures" (SciPost Phys. 16, 055).
Symmetry requirements
The search for superconducting systems exhibiting nonreciprocal transport and the diode effect has proliferated, encompassing planar hybrid structures, asymmetric SQUIDs and certain noncentrosymmetric superconductors. A common feature is gyrotropic symmetry, realized on different scales and characterized by a polar vector. Alongside time-reversal symmetry breaking, the presence of a polar axis allows magnetoelectric effects which, when combined with proximity-induced superconductivity, result in spontaneous non-dissipative currents that underpin the diode effect.
Proposed device and theory
The authors present a comprehensive theoretical study of transport in a lateral Josephson junction composed of a normal metal supporting the spin Hall effect, attached to a ferromagnetic insulator. Because of the ferromagnetic insulator, magnetoelectric effects arise without requiring external magnetic fields. The theory determines the dependence of the anomalous currents on the spin relaxation length and on transport parameters commonly used in spintronics to characterize the metal/ferromagnetic-insulator interface. It thereby unifies nonreciprocal transport in superconducting systems with classical spintronic effects: the spin Hall effect, the spin galvanic effect and spin Hall magnetoresistance.
Proposed experiment
The authors propose an experiment involving measurements of magnetoresistance in the normal state and nonreciprocal transport in the superconducting state. Such an experiment would allow determination of the model parameters, verifying theories of magnetoelectric effects in normal systems with greater precision, and would contribute to a deeper understanding of the microscopic origins that determine those parameters.
Source notes & attribution
- https://rexresearch.com/CISSMetamaterial/CISSMetamaterial.html