Degenerate monolayer Ising superconductors via chiral-achiral molecule intercalation

TL;DR

This study demonstrates that molecule-intercalated TaS2 and NbSe2 exhibit monolayer-like Ising superconductivity with preserved inversion symmetry, revealing the roles of interlayer decoupling and charge transfer in their superconducting properties.

Contribution

It provides controlled, device-integrated evidence that intercalation induces monolayer-like superconductivity without unconventional pairing, clarifying the effects of interlayer decoupling and symmetry.

Findings

Intercalation induces interlayer decoupling in TaS2, leading to Ising superconductivity.

NbSe2 retains quasi-3D transport with gradual Ising enhancement.

Transport remains reciprocal, indicating preserved inversion symmetry.

Abstract

Engineering unconventional superconductors is a central challenge in condensed matter physics. Molecule-intercalated TaS2 superlattices have recently been reported to host such states, yet their origin remains debated, underscoring the urgent need for controlled, device-integrated studies. Here, we report that nanometer-thick TaS2 and NbSe2 intercalated with chiral and achiral organic cations instead exhibit robust monolayer-like Ising superconductivity, with no evidence of unconventional pairing. Using high-quality superlattices integrated into devices, we disentangle the roles of interlayer coupling and charge transfer in shaping their superconducting behavior. In TaS2, intercalation induces interlayer decoupling regardless of molecular size or symmetry, yielding monolayer-like Ising superconductivity. NbSe2 instead retains quasi-three-dimensional transport, with a gradual Ising enhancement and near-monolayer behavior only at the largest interlayer spacing. Transport remains reciprocal across all superlattices, consistent with preserved inversion symmetry and incompatible with parity-breaking superconductivity and noncentrosymmetric monolayers. We attribute the behavior to electronically detached monolayers with opposite spin-split bands, coupled through thermal and tunneling processes, which overall preserve inversion symmetry. These findings establish molecular intercalation compounds as a robust, device-ready, platform for engineering advanced superconducting superlattices.