Field dependence of the vortex core size probed by STM

Abstract

We study the spatial distribution of the density of states (DOS) at zero bias N(r) in the mixed state of single and multigap superconductors. We provide an analytic expression for N(r) based on deGennes' relation between DOS and the order parameter that reproduces well Scanning Tunneling Microscopy (STM) data in several superconducting materials. In the single gap superconductor $\beta$-Bi${}_2$Pd, we find that N(r) is governed by a length scale ${\xi }_H=\sqrt{{\varphi }_0/2\pi H}$, which decreases in rising fields. The vortex core size $\mathcal{C}$, defined via the slope of the order parameter at the vortex center, $\mathcal{C}$ $\propto (d\Delta /dr{|}_{r\to 0}{)}^{-1}$, differs from ${\xi }_H$ by a material dependent numerical factor. For two gap superconductors 2H-NbSe${}_{1.8}$S${}_{0.2}$ and 2H-NbS${}_2$, we find that $\mathcal{C}$ is field independent and has the same value for both bands. We conclude that, independently of the magnetic field induced variation of the order parameter values in both bands, the spatial variation of the order parameter close to the vortex core is the same for all bands.

8 pages, 9 figures

References in corpus (8)

• Scanning tunneling spectroscopy of high-temperature superconductors
• Superconducting density of states and vortex cores of 2H-NbS2
• Scanning Tunneling Microscopy/Spectroscopy of Vortices in LiFeAs
• Intrinsic atomic scale modulations of the superconducting gap of 2H-NbSe2
• Two-band superconductors: Hidden criticality deep in the superconducting state
• Pressure dependence of superconducting critical temperature and upper critical field of 2H-NbS2
• Scanning tunneling spectroscopy with superconducting tips of Al
• Ubiquitous V-shape density of states in mixed state of clean limit type II superconductors; STM experiment and theory

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