Orbital-selective two-dimensional superconductivity in 2H-NbS_{2}

Abstract

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 2H-NbS_{2} flakes, we observe a cusp peak associated with a 2D superconducting subband from the d_{xy} and d_{x^{2}−y^{2}} orbitals of Nb atoms, and a round peak related to a 3D subband, directly confirming the existence of intrinsic 2D superconductivity in 2H-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.