Realizing a Superconducting Square-Lattice Bismuth Monolayer

Abstract

Interplay of crystal symmetry, strong spin−orbit coupling (SOC), and many-body interactions in low-dimensional materials provides a fertile ground for the discovery of unconventional electronic and magnetic properties and versatile functionalities. Two-dimensional (2D) allotropes of group 15 elements are appealing due to their structures and controllability over symmetries and topology under strong SOC. Here, we report the heteroepitaxial growth of a proximityinduced superconducting 2D square-lattice bismuth monolayer on superconducting Pb films. The square lattice of monolayer bismuth films in a C 4 symmetry together with a stripey moireś tructure is clearly resolved by our scanning tunneling microscopy, and its atomic structure is revealed by density functional theory (DFT) calculations. A Rashba-type spin-split Dirac band is predicted by DFT calculations to exist at the Fermi level and becomes superconducting through the proximity effect from the Pb substrate. We suggest the possibility of a topological superconducting state in this system with magnetic dopants/field. This work introduces an intriguing material platform with 2D Dirac bands, strong SOC, topological superconductivity, and the moirésuperstructure.

Structures of α-BixSb1–x Alloys Formed on the TiSe2 Substrates

“…4 Eunseok and co-workers observed the proximityinduced superconducting gap in α-Bi grown on Pb(111). 5 Very recently, Gou et al reported the ferroelectric states in monolayer α-Bi, in which the ordered charge transfer and the regular atom distortion between sublattices happen simultaneously. 6 It is clear that the coupling with the substrate greatly affects the detailed structures of Bi and Sb and thus modulates their physical properties.…”

“…Li et al observed a charge density wave (CDW) without periodic lattice distortion in α-Sb, which is assigned to the unique feature of the excitonic insulator . Eunseok and co-workers observed the proximity-induced superconducting gap in α-Bi grown on Pb(111) . Very recently, Gou et al reported the ferroelectric states in monolayer α-Bi, in which the ordered charge transfer and the regular atom distortion between sublattices happen simultaneously .…”

“…Indeed, great efforts have been made to achieve controllable growth of the α- and β-phases of Bi and Sb on different substrates. In recent years, α-Bi was successfully grown on various substrates, e.g., group-IVA monocrystal (highly oriented pyrolytic graphite, Si(111), Pb(111)), transition metal dichalcogenides (NbSe 2 , TiSe 2 , HfTe 2 ), and ferromagnetic materials (Cr 2 Ge 2 Te 6 , Fe 3 GeTe 2 ). α-Sb was also prepared on a variety of substrates, such as WTe 2 and SnSe .…”

Periodic stacking of two dimensional Bismuth bi-layers in Bismuth stearate thin films

“…Very recent theoretical and experimental investigations have demonstrated Bi-induced (both single and bi-layer) interesting modifications of the electronic states of the semiconductor substrate surface on which the single or bi-layer Bi is deposited [12,13]. In some cases, such a 2D single Bi layer on the substrate surface has been shown to exhibit exotic electronic states like one-dimensional electron channels [14] and 2D topological superconducting states [15]. In our earlier work, we were able to deposit Bi-bi-layer on a three-dimensional topological insulator Bi 2 Se 3 substrate by in-situ exposure of the substrate surface to atomic hydrogen [16].…”