Superconducting ferecrystals: turbostratically disordered atomic-scale layered (PbSe)1.14(NbSe2)n thin films

Abstract

Hybrid electronic heterostructure films of semi- and superconducting layers possess very different properties from their bulk counterparts. Here, we demonstrate superconductivity in ferecrystals: turbostratically disordered atomic-scale layered structures of single-, bi- and trilayers of NbSe2 separated by PbSe layers. The turbostratic (orientation) disorder between individual layers does not destroy superconductivity. Our method of fabricating artificial sequences of atomic-scale 2D layers, structurally independent of their neighbours in the growth direction, opens up new possibilities of stacking arbitrary numbers of hybrid layers which are not available otherwise, because epitaxial strain is avoided. The observation of superconductivity and systematic Tc changes with nanostructure make this synthesis approach of particular interest for realizing hybrid systems in the search of 2D superconductivity and the design of novel electronic heterostructures.

Superconducting Tin Selenide/Niobium Diselenide Ferecrystals†

“…The characteristic temperature dependence of the resistivity at the transition from the normal to superconducting state remains identical and it occurs at the same critical temperature, even though the absolute resistance value of the different samples may vary due to defects or stacking faults. Furthermore, neither the in‐plane polycrystallinity of the NbSe 2 layers nor differences in polytype can be considered a cause for such a strong reduction in T c alone as was recently discussed in detail …”

“… in dependence of m for [(SnSe) 1+δ ] m (NbSe 2 ) 1 ferecrystals in comparison to ferecrystals [(PbSe) 1+ δ ] 1 (NbSe 2 ) 1 , conventional misfit layer compounds (MLCs) reported by Nader et al . and Auriel et al .…”

“…The T c for the compound in which the single NbSe 2 layers are separated by PbSe layers, [(PbSe) 1+x ] 1 (NbSe 2 ) 1 shows a close value as [(SnSe) 1.16 ] 1 (NbSe 2 ) 1 ferecrystal, if taken in the misfit layer compound configuration ( T c = 2.5 K), while that for the [(PbSe) 1+x ] 1 (NbSe 2 ) 1 ferecrystal is further suppressed ( T c = 1.11(2) K). This indicates the sensitive role that the choice of the PbSe or SnSe interlayer in connection with turbostratic disorder plays in the formation of the superconducting state.…”

Superlattices based on van der Waals 2D materials

“…Elements of the unit cell Modulation by (dimension) Applications (ref. ) Vertical stacking Chemical composition, lattice (mis)match (1D) IR photodetectors 15,16,20 Phase-change memory [28][29][30][31][32][33][34] Thermoelectrics [47][48][49][50] Superconductivity [51][52][53][54] Intercalated compounds Chemical composition, structuring, charge transfer (1D)…”

“…54 Fig. 2(b) and (c) show, respectively, the cross-sectional TEM images of a misfit layer compound 51 and ferecrystal 53 superconducting superlattice.…”