Affiliation
Consejo Superior de Investigaciones Científicas
Title of work
Majorana-like Coulomb spectroscopy in the absence of zero bias peaks
Abstract
Coulomb Blockade spectroscopy (CBS) is a powerful complement to Tunneling spectroscopy (TS) in the search for Majorana bound states (MBSs) in hybrid nanowires. Of particular interest are full-shell nanowires, which exhibit the characteristic Little-Parks effect. Recent experiments on full-shell nanowires showed CBS results compatible with Majorana zero modes exponentially protected by nanowire length, with zero-bias peaks visible in TS, albeit in different devices. Here we combine for the first time both techniques on the same device, and find the CBS can appear Majorana-like even in the absence of zero bias peaks (ZBPs), making the two techniques questionable when applied individually. Our CBS results depend on wire length, but also on confinement barriers, which is unexpected from protected MBSs. We explain our observations in terms of a quasicontinuum of subgap states produced by the winding of superconducting phase in nonzero Little-Parks lobes. This quasicontinuum merges into a smooth subgap background in TS configurations, without any visible peaks.