Magnetic field orientation dependence of planar tunneling spectroscopy in the superconducting state of NbSe 2

Layered superconductors exhibit strong anisotropic responses to magnetic fields in out-of-plane and in-plane orientations, due to their distinct vortex structures and upper critical field values. Here, we utilize the planar tunnel junction technique to perform continuous magnetic field-dependent d I /d V spectroscopy measurements on 2H-NbSe 2 under different field orientations. We observe characteristic kink features for weak in-plane magnetic fields, but the overall behaviors are quite similar for different field orientations despite the distinct vortex generation processes and widely different upper critical field values. Especially, the generic square root dependence of the Fermi level density of state on magnetic field indicates that the Doppler shift plays a central role in the low energy excitations of 2H-NbSe 2 in the presence of magnetic field.