Spin-Orbit Locking as a Protection Mechanism of the Odd-Parity Superconducting State against Disorder

Unconventional superconductors host a plethora of interesting physical phenomena. However, the standard theory of superconductors suggests that unconventional pairing is highly sensitive to disorder, and hence can only be observed in ultraclean systems. We find that due to an emergent chiral symmetry, spin-orbital locking can parametrically suppress pair decoherence introduced by impurity scattering in odd-parity superconductors. Our work demonstrates that disorder is not an obstacle to realize odd-parity superconductivity in materials with strong spin-orbit coupling.

Figure 1

The effect of disorder on the single particle Green’s function and pair susceptibility. The self-consistent equation for the self-energy [Eq. (7)] is illustrated in (a). The double line represents the dressed electron Green’s function, and the dashed line denotes the impurities. The equation for the Cooperon [Eq. (9)] is illustrated in (b). Here, the Cooperon is drawn as a filled triangle vertex.

Figure 2

The critical temperature as a function of the level of disorder $\pi {\nu }_0{V}_{\mathrm{imp}}^2$ for various values of $\alpha$. Both $T_c$ and $\pi {\nu }_0{V}_{\mathrm{imp}}^2$ are given in units of of $T_c^0$, the critical temperature for $V_{\mathrm{imp}}=0$. For comparison, the dashed line shows the transition temperature into the odd-parity superconducting state in the absence of spin-orbital locking (as in Helium-III). One can see that up to $\alpha \approx 0.5$ the critical level of disorder in which the unconventional order parameter disappears is dramatically higher than in Helium-III.