Tuning metal/superconductor to insulator/superconductor coupling via control of proximity enhancement between NbSe2 monolayers

Abstract

The interplay between charge transfer and electronic disorder in transition-metal dichalcogenide multilayers gives rise to superconductive coupling driven by proximity enhancement, tunneling and superconducting fluctuations, of a yet unwieldy variety. Artificial spacer layers introduced with atomic precision change the density of states by charge transfer. Here, we tune the superconductive coupling between NbS e 2 monolayers from proximity-enhanced to tunneling-dominated. We correlate normal and superconducting properties in SnSe 1 + δ m NbS e 2 1 tailored multilayers with varying SnSe layer thickness ( m = 1 − 15 ). From high-field magnetotransport the critical fields yield Ginzburg-Landau coherence lengths with an increase of 140 % cross-plane ( m = 1 − 9 ), trending towards two-dimensional superconductivity for m > 9 . We show cross-overs between three regimes: metallic with proximity-enhanced coupling ( m = 1 − 4 ), disordered-metallic with intermediate coupling ( m = 5 − 9 ) and insulating with Josephson tunneling ( m > 9 ). Our results demonstrate that stacking metal mono- and dichalcogenides allows to convert a metal/superconductor into an insulator/superconductor system, prospecting the control of two-dimensional superconductivity in embedded layers.