2025/06/11 by Chandan Patra, Patra, Chandan, Tarushi Agarwal +14 · 1 citation
Materials Science · Physics and Astronomy · #2D Materials and Applications #Iron-based superconductors research #Topological Materials and Phenomena
paper · pdf · doi:10.48550/arxiv.2506.09413
Transition metal dichalcogenides exhibit multiple polymorphs that enable the exploration of diverse quantum states, including valley-selective spin polarization, the valley Hall effect, Ising superconductivity, and nontrivial topology. Monolayer 2H-NbSe2 is a promising candidate for realizing Ising superconductivity due to its spin-split, out-of-plane spin-polarized states arising from inversion symmetry breaking and strong spin-orbit coupling. In contrast, bulk 2H-NbSe2 retains inversion symmetry and lacks spin splitting, limiting its suitability for hosting Ising superconductivity. Here, we report the growth of high-quality single crystals of the acentric bulk superconducting polymorph, 4H-NbSe2, which intrinsically breaks the inversion symmetry and supports valley-selective spin-polarized states. Magnetization and resistivity measurements reveal anisotropic superconductivity, with the in-plane upper critical field exceeding the Pauli limit, while out-of-plane fields suppress superconductivity more rapidly, before reaching the Pauli limit, which strongly suggests the presence of Ising pairing. First-principles calculations and symmetry analysis confirm significant valley-selective spin splitting with out-of-plane spin polarization, further supporting the emergence of Ising superconductivity in 4H-NbSe2. These results establish 4H-NbSe2 as a robust bulk platform to investigate Ising superconductivity and valley-selective phenomena in transition-metal dichalcogenides.