Superconducting diode effect due to magnetochiral anisotropy in topological insulators and Rashba nanowires

Abstract

The critical current of a superconductor can depend on the direction of current flow due to magnetochiral anisotropy when both inversion and time-reversal symmetry are broken, an effect known as the superconducting (SC) diode effect. Here, we consider one-dimensional (1D) systems in which superconductivity is induced via the proximity effect. In both topological insulator and Rashba nanowires, the SC diode effect due to a magnetic field applied along the spin-polarization axis and perpendicular to the nanowire provides a measure of inversion symmetry breaking in the presence of a superconductor. Furthermore, a strong dependence of the SC diode effect on an additional component of magnetic field applied parallel to the nanowire as well as on the position of the chemical potential can be used to detect that a device is in the region of parameter space where the phase transition to topological superconductivity is expected to arise.

Parity protected superconducting diode effect in topological Josephson junctions

“…Note that, within our Rashba nanowire model, the SC diode effect is only present when ∆x = 0, ∆y = 0, and α = 0 are all satisfied, since these are necessary to manifest both broken inversion and time-reversal symmetry, see similar discussions in Ref. [86,100]. (c-d) In the topological phase, ∆x > ∆0, MBSs begin to form and a much larger SC diode effect is present.…”

“…(a-b) When the junction is in the trivial phase, ∆x < ∆0 for our parameters, only a weak SC diode effect is present, even for junctions with visible deviations from a purely sinusoidal CPR, see also Fig.4(a-b). Note that, within our Rashba nanowire model, the SC diode effect is only present when ∆x = 0, ∆y = 0, and α = 0 are all satisfied, since these are necessary to manifest both broken inversion and time-reversal symmetry, see similar discussions in Ref [86,100]…”

“…At finite flux Φ, a large parity-protected SC diode effect occurs when the junction is in the topological phase. ticular, magnetochiral anisotropy of the energy spectrum can result in a critical current of a material or junction that is dependent on the direction of current flow and applied magnetic field [79,86,97]. This results in a range of current for which supercurrent can flow only in one direction through the material or junction.…”

“…In the bulk of proximitized nanowires this effect can be used, e.g. to determine the direction of the SOI vector and provide a measure of the strength of the SOI in the presence of a superconductor [86,91,97].…”

Superconducting Diode Effect -- Fundamental Concepts, Material Aspects, and Device Prospects

“…Following these intriguing experimental observations, and inspired by theoretical work by V. M. Edelstein [26][27][28], SDE has been theorized by a number of research groups. For instance, by employing mean-field (MF), Bogoliubov-de Gennes (BdG) and Ginzburg-Landau (GL) theories, theoretical insights have recently been presented for SDE in junction-free bulk SCs [29][30][31][32][33][34][35][36][37][38] as well as for its JJ version [39][40][41][42][43][44][45]. Though, the intrinsic mechanism to cause SDE in junction-free SCs is recently clarified, i.e., nonreciprocity of depairing critical current, theoretical modelling for potential spin-orbit coupled bulk SCs is still enjoying its infancy [29][30][31][32][33][34][35][36][37][38].…”