Orbital-selective two-dimensional superconductivity in 2H−NbS2

Orbital-selective superconductivity is crucial for understanding the pairing mechanism for multiband superconductors. Atomic $d$ orbitals with anisotropic spatial extension can directly determine the energy dispersion of subbands with two-dimensional (2D) or three-dimensional (3D) nature in band structure. Theoretically, owing to the coexistence of these 2D and 3D subbands, the orbital-selective superconductivity can exhibit band-dependent dimensionality in multiband superconductors. However, to experimentally confirm this orbital-selective 2D superconductivity remains challenging and elusive. Herein, based on angle-dependent upper critical magnetic field on $2\mathrm{H}\text{\ensuremath{-}}{\mathrm{NbS}}_{2}$ flakes, we observe a cusp peak associated with a 2D superconducting subband from the ${d}_{xy}$ and ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$ orbitals of Nb atoms, and a round peak related to a 3D subband, directly confirming the existence of intrinsic 2D superconductivity in $2\mathrm{H}\text{\ensuremath{-}}{\mathrm{NbS}}_{2}$ thick flake and its orbital-selective superconducting nature. The 2D superconductivity remains robust under large electric current or high pressure. Such observations shed light on the orbital-selective pairing mechanism and resulting band-dependent dimensionality for multiband superconductors.