• Accepted Paper

Reduced pair breaking from extended disorder in unconventional superconductors: Implications for 4Hb-TaS2

Yuval Tsur, Mark H. Fischer, and Jonathan Ruhman

Phys. Rev. B - Accepted 22 September, 2026

DOI: https://doi.org/10.1103/kmyj-rmpt

Abstract

Unconventional superconductivity is generally expected to be strongly suppressed by nonmagnetic disorder, as captured by Abrikosov–Gor’kov (AG) theory. However, several materials, including transition metal dichalcogenides, exhibit signatures of unconventional pairing despite relatively high resistivities, suggesting a breakdown of the conventional relation between momentum relaxation and pair breaking. Here, we study this problem in H-phase transition metal dichalcogenides by computing the disorder-dressed pairing susceptibility. We employ a multiband model with spin-orbit coupling and include an impurity potential that mimics a common lattice defect, namely a chalcogen vacancy or site ad-atom. This yields to an extended impurity potential, which we compare with the commonly considered on-site (point defect) potential. We evaluate the momentum-relaxation rate and the pair-breaking rate on equal footing. We find that extended impurity potentials lead to a parametrically reduced pair-breaking rate compared to the transport scattering rate, with ΓτD∼1/3 over a wide parameter range. This reduction originates from the momentum structure of the disorder potential, which partially matches the internal structure of the superconducting gap and suppresses pair-breaking processes. As a result, unconventional pairing states are significantly more robust than predicted by standard AG theory. Our results provide a natural explanation for the persistence of unconventional superconductivity in systems with strong disorder and substantially alleviate the apparent conflict between high resistivity and unconventional pairing in materials such as 4Hb-TaS2.

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