Fig. 4: Local noise spectroscopy on and off vortices in NbSe2 and FeTe0.55Se0.45.
From: Single-electron charge transfer into putative Majorana and trivial modes in individual vortices
a, c Current noise spectra in the tunnel junction (with a resistance RJ = 2.5 MOhm) taken on (red) and off (blue) the vortex shown in Fig. 2a for NbSe2 and Fig. 3a for FeTe0.55Se0.45, respectively. The locations of these spectra are marked by the crosses in Figs. 2a and 3a with the same colors. Gray curves are the expected noise from Eq. 2 with an effective charge q* of 1e and 2e at T = 2.3 K. The dashed lines in a and c are replicated from Figs. 2b and 3b, respectively, serving as guides for the coherence peaks (red and blue) and the bound states (gray). The error bars are determined by the fluctuation of the current noise in time before each experiment, yielding a standard deviation of 9.25 and 6.77 fA2/Hz for a and c, respectively. b, d Effective charge q* derived by numerically solving Eq. 2 at the energy E = ±Δt on (red) and off (blue) vortex for three different vortices in NbSe2 and FeTe0.55Se0.45, respectively. The error bars are determined by the standard deviation of the extracted q* (Supplementary Figs. 3–5) in the energy ranges (Δt ± 0.1 meV) and -(Δt ± 0.1 meV).
