Supercurrent diode effect and finite-momentum superconductors

Abstract

Significance Our work shows a fascinating application of finite-momentum superconductivity, the supercurrent diode effect, which is being reported in a growing number of experiments. We show that, under external magnetic field, Cooper pairs can acquire finite momentum so that critical currents in the direction parallel and antiparallel to the Cooper pair momentum become unequal.

The Josephson diode effect in supercurrent interferometers

“…This property of the CPR ensures that the critical currents for the two current-bias directions, I + c and I − c , are equal so that a JD effect is missing. To circumvent this symmetry constraint, previous works have observed and studied a diode effect in inversion-symmetry breaking superconducting thin films [1][2][3][4][5][6], JJs of finite-momentum pairing superconductors [7][8][9], JJs of multi-layered materials [10][11][12][13][14], topological insulator JJs [15,16], and JJs with a spin-orbit coupled two-dimensional electron gas subject to a Zeeman field [17][18][19]. Moreover, it was also noted that a diode effect can arise in spin-orbit coupled nanowire JJs subject to a Zeeman field [20][21][22][23], magnetic junctions [24][25][26], and domain wall SC channels [27].…”

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

“…It has been shown that normal state rectification due to MCA can have a counterpart in the superconducting (SC) phase [10][11][12]. Namely, when a current flows in a superconductor where both time reversal and inversion symmetry are broken, the critical current density at which breakdown of superconductivity occurs can be non-reciprocal too, such that j + c = |j − c | [11][12][13][14][15][16][17][18][19][20], where ± indicates the direction of current flow and relative sign of critical current (see Fig. 1).…”

“…Recently it has been shown that the SC diode effect can be described phenomenologically using a finite pairingmomentum [16][17][18] and we will follow a similar formulation here. While some aspects may not be captured by this treatment, these theories of the SC diode effect are sufficient to understand the behaviour expected in the nanowire systems considered here.…”

“…However, the spectrum becomes fully gapless for any q above the positive (q + ) or below the negative (q − ) critical pairing momentum [see Fig. 3(a)] meaning that tanh(βE η,k,q /2) = 0 at certain values of momentum k, as a result j(q) deviates from the linear behaviour which indicates the breakdown of superconducting phase at this momentum [16][17][18].…”

“…( 5), and, using Eq. ( 6), obtain the maxima (j + c ) and minima (j + c ) of j(q), which corresponds to the extremal supercurrent after which the superconductivity in the nanowire becomes fully gapless [16][17][18]. In the topological transition regime an accidental gap clos- ing can also occur at the supercurrent induced transition from trivial to topological superconductivity [51][52][53][54][55], however, we focus on the maximal supercurrent the proximitized nanowire can maintain.…”