Field-Independent Superconducting Diode Effect and Field-Dependent Rectification Effect in Iron-Based Superconductors

The superconducting diode effect (SDE), where zero resistivity is realized in one current flow direction whereas non-zero resistivity in the opposite direction, is gathering tremendous fascination in both fundamental and applied physics because the SDE is a novel phenomenon resulting from symmetry breaking and enables the creation of low-power and low-noise electric circuit. Recently, a field-free SDE originating from a thermoelectric effect was reported in iron-based superconductors with nonmagnetic electrodes1). Since amount of the research of the field-free SDE is very limited despite its importance in the perspective of symmetry breaking and possible realization of compact superconducting circuit without magnetic field, further understandings of the physical properties about the thermoelectric SDE are desired. Here, we investigate the SDE where ferromagnetic electrodes are equipped with iron-based superconductors to study the response of the SDE in the combination of an external magnetic field and ferromagnetic electrodes. Whereas the field-free thermoelectric SDE is dominant in the devices, the field-dependent and non-linear rectification effect are superimposed. The possible origin of the rectification is superposition of the two types of effects originating from Rashba type spin-orbit interaction.