Supercurrent diode effect and magnetochiral anisotropy in few-layer NbSe$_2$

Abstract

Nonreciprocal transport refers to charge transfer processes that are sensitive to the bias polarity. Until recently, nonreciprocal transport was studied only in dissipative systems, where the nonreciprocal quantity is the resistance. Recent experiments have, however, demonstrated nonreciprocal supercurrent leading to the observation of a supercurrent diode effect in Rashba superconductors, opening the vision of dissipationless electronics.Here we report on a supercurrent diode effect in NbSe 2 nanowires obtained by patterning NbSe 2 flakes with odd layer number. The observed rectification is driven by valley-Zeeman spin-orbit interaction. We demonstrate a rectification efficiency as large as 33%, considerably larger than the efficiency of devices based on Rashba superconductors. In agreement with recent theory for superconducting transition metal dichalcogenides, we show that the effect is driven by an out-of-plane magnetic field component. Remarkably, we find that the effect becomes field-asymmetric in the presence of an additional in-plane field component transverse to the current direction. Supercurrent diodes offer a further degree of freedom in designing superconducting quantum electronics with the high degree of integrability offered by van der Waals materials.

Effect of Rashba and Dresselhaus spin-orbit coupling on supercurrent rectification and magnetochiral anisotropy of ballistic Josephson junctions

“…In both cases, the SOI was of Rashbatype and the supercurrent rectification driven by the in-plane field perpendicular to the current. Very recent reports [25,26] have demonstrated the supercurrent diode effect in a system (few-layer NbSe 2 ) with valley-Zeeman SOI, where the rectification is driven by the out-of-plane field, as expected from theory [27]. As discussed in our previous work [23], in JJs with Rashba SOI, the supercurrent diode effect is strictly related to the ϕ 0 shift discussed above.…”

Universal Josephson diode effect

“…To obtain the amplitudes of Andreev reflection, we solve the condition on the scattering states  N (1,2) = s A | x=0,d  S (1,2) at each interface (x = 0 and x = d) using the solutions to the Schrodinger equation in each region. We solve these equations for incoming electrons and holes and obtain the matrix describing Andreev scattering at both interfaces…”

“…Recently, there has been a surge of interest in nonreciprocal phenomena in superconductors. In particular, recent experiments have observed an asymmetry between forward and reverse critical currents I c+ ≠ I c− in superconducting films (1)(2)(3) and Josephson junctions (4)(5)(6)(7)(8). In the presence of such a nonreciprocity, currents of magnitudes in the range between I c+ and I c− can flow without resistance in only one direction, resulting in supercurrent diode effect.…”

Hybrid helical state and superconducting diode effect in S/F/TI heterostructures

“…The superconducting diode effect has been predicted for homogeneous materials with SOC and finite-momentum helical ground state [51][52][53][54][55] , S/F bilayers with interface spin-orbit coupling 56 and for Josephson junctions 28,57,58 . It has been also observed in superconducting films, layered systems without a centre of inversion [59][60][61] and Josephson junctions [62][63][64][65][66][67][68][69] . Here we investigate it in the topological insulator based systems and obtain that the value of the nonreciprocity defined as (I c+ − I c− )/(I c+ + I c− ) is of the order of unity, thus demonstrating that the 3D TI -based systems are very perspective for studying magnetoelectric effects and nonreciprocity.…”