Tilted vortex cores and superconducting gap anisotropy in 2H-NbSe2

Abstract

Superconducting vortex cores have been extensively studied for magnetic fields applied perpendicular to the surface by mapping the density of states (DOS) through Scanning Tunneling Microscopy (STM). Vortex core shapes are often linked to the superconducting gap anisotropy---quasiparticle states inside vortex cores extend along directions where the superconducting gap is smallest. The superconductor 2H-NbSe${}_2$ crystallizes in a hexagonal structure and vortices give DOS maps with a sixfold star shape for magnetic fields perpendicular to the surface and the hexagonal plane. This has been associated to a hexagonal gap anisotropy located on quasi two-dimensional Fermi surface tubes oriented along the $c$ axis. The gap anisotropy in another, three-dimensional, pocket is unknown. However, the latter dominates the STM tunneling conductance. Here we measure DOS in magnetic fields parallel to the surface and perpendicular to the $c$ axis. We find patterns of stripes due to in-plane vortex cores running nearly parallel to the surface. The patterns change with the in-plane direction of the magnetic field, suggesting that the sixfold gap anisotropy is present over the whole Fermi surface. Due to a slight misalignment between the vector of the magnetic field and the surface, our images also show outgoing vortices. Their shape is successfully compared to detailed calculations of vortex cores in tilted fields. Their features merge with the patterns due to in plane vortices, suggesting that they exit at an angle with the surface. Measuring the DOS of vortex cores in highly tilted magnetic fields with STM can thus be used to study the superconducting gap structure.

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• Determining the vortex tilt relative to a superconductor surface
• Observation of an in-plane vortex lattice transition in the multiband superconductor 2H-NbSe2 using scanning tunneling spectroscopy

Cited by in corpus (13)

• Direct visualization of the nematic superconductivity in Cu${}_x$Bi${}_2$Se${}_3$
• Tunneling into the vortex state of NbSe${}_2$ with van der Waals junctions
• The effect of Sn intercalation on the superconducting properties of 2H-NbSe2
• Strain-induced stripe phase in charge ordered single layer NbSe${}_2$
• Robustness of Yu-Shiba-Rusinov resonances in presence of a complex superconducting order parameter
• Absence of superconducting dome at the charge-density-wave quantum phase transition in 2H-NbSe2
• Unveiling hidden charge density waves in single-layer NbSe${}_2$ by impurities
• Fast multifrequency measurement of nonlinear conductance
• Microscopic Eilenberger theory of Fulde-Ferrell-Larkin-Ovchinnikov states in the presence of vortices
• Thermal creep emerging from cooling a tilted vortex lattice in uniaxial superconductor
• Vortex lattices and critical fields in anisotropic superconductors
• Hall Effect for Dirac Electrons in Graphene Exposed to an Abrikosov Flux Lattice
• Scanning Tunneling Microscopy in high vectorial magnetic fields