Ubiquitous Superconducting Diode Effect in Superconductor Thin Films

Abstract

A superconductor exhibiting a polarity-dependent critical current is of fundamental as well as technological interest, because the superconducting (SC) layer can then admit a perfect dissipationless transmission along one direction while offering a large resistance along the opposite, leading to a phenomenon called SC diode effect or rectification. Here we demonstrate that SC diode effects are ubiquitous in superconductors and observable in a large variety of settings. Controllable via an out-of-plane magnetic field, we observe an extremely sensitive SC diode effect (type A) in superconducting vanadium or niobium stripes with symmetry breaking between their two edges. Nonreciprocity of critical current results from an out-of-plane field as small as 1 Oe, while the diode efficiency and polarity are manipulated via the strength and direction of the field. With the out-of-plane field carefully eliminated, an in-plane field also creates a sizeable asymmetry between critical currents (type B), regardless of whether this field is perpendicular or parallel to the current flow direction. Finally, we demonstrate nonreciprocal critical currents with a giant diode efficiency reaching 65% when the SC V film couples to a ferromagnetic EuS layer with in-plane magnetization orthogonal to current flow (type C) and a clear diode rectification is seen. This is also realized at zero applied field, in the remnant magnetic state of EuS. Our observations show the ubiquity of the superconducting diode effect, and pave the way for the development of versatile SC rectifiers employing simple structures using widely available materials.

Magnetization Control of Zero‐Field Intrinsic Superconducting Diode Effect

“…When superconductivity breaks from the edge of the sample, the sign of Q should change depending on which end of the sample the superconductivity starts to break from. First, we verified the contribution of asymmetric edges [ 14 ] by examining the reproducibility of Q . As shown in Figure S4 (Supporting Information), we confirmed that the values of | Q | are reproduced at ≈40%, and the sign of the zero‐field SDE does not change.…”

Superconducting diode effect in quasi-one-dimensional systems

“…Recently, the observation of non-reciprocity in the critical current of superconductors, known as the superconducting diode effect (SDE) [1][2][3], has brought attention to this phenomenon for its potential to achieve dissipationless electronics. Following the initial observations, extensive work has been done to show the signature of SDE in different bulk materials [4][5][6][7][8]. This diode effect was also observed and thoroughly studied in Josephson junctions [9][10][11][12][13][14][15][16] (first in the context of the anomalous Josephson effect [17][18][19][20][21]) and even in the absence of an applied magnetic field [22][23][24][25][26].…”

Nonreciprocal Supercurrents in a Field-Free Graphene Josephson Triode

“…In the meantime, it has been realized that higher superconducting diode efficiency can be achieved in properly designed nanostructures in which the time-reversal symmetry is broken via trapped fluxes or an external magnetic field. − However, a magnetic field is often undesired for integrating the devices in superconducting circuits. In this work, we rectify this problem by creating superconducting diodes which can operate at zero external magnetic field and achieve efficiency approaching 100%.…”