Superconductivity in gallenene

Abstract

Among the large variety of two-dimensional (2D) materials discovered to date, elemental monolayers that host superconductivity are very rare. Using ab initio calculations we show that recently synthesized gallium monolayers, coined gallenene, are intrinsically superconducting through electron-phonon coupling. We reveal that Ga-100 gallenene, a planar monolayer isostructural with graphene, is the structurally simplest 2D superconductor to date, furthermore hosting topological edge states due to its honeycomb structure. Our anisotropic Eliashberg calculations show distinctly three-gap superconductivity in Ga-100, in contrast to the alternative buckled Ga-010 gallenene which presents a single anisotropic superconducting gap. Strikingly, the critical temperature (Tc) of gallenene is in the range of 7 − 10 K, exceeding the Tc of bulk gallium from which it is exfoliated. Finally we explore chemical functionalization of gallenene with hydrogen, and report induced multigap superconductivity with an enhanced Tc in the resulting gallenane compound.

Enhancing superconductivity in MXenes through hydrogenation

“…8,27,28 Moreover, the hydrogenated MXenes studied here present another important class of 2D materials in which hydrogen adatoms boost the EPC and the superconducting T c , extending significantly prior results for p-doped graphane, 29 hydrogenated monolayer MgB 2 , 14 and hydrogenated gallium monolayers (gallenane). 15…”

“…This principle has been demonstrated through ab initio calculations for hydrogenated monolayer MgB 2 14 – with a T c of 67 K, which can be boosted to over 100 K by applying biaxial tensile strain – as well as for the elemental 2D material gallenene. 15 These systems inherit the stability of the 2D host material, while at the same time they are very rich in hydrogen, as needed for a sizeable effect on the superconducting properties. The enhancement of the EPC originates from (i) hybridization between electronic and vibrational states of hydrogen and the host atoms, and (ii) emerging ultrahigh frequency modes of hydrogen, expanding the frequency range of the EPC.…”

Stability and electronic properties of gallenene

“…Similar values of the critical temperature are a result of similarity of phonon frequencies and electron–phonon coupling coefficients in different gallenene structures. A recent relevant paper 34 brought to our attention after the submission of the present work has estimated the T c to be 7–10 K for the structures taken from ref. 8 (unstable 10 and metastable 14 1 in our notations, Fig.…”

Single-Element 2D Materials beyond Graphene: Methods of Epitaxial Synthesis

“…Aluminene and antimonene are proposed as materials for creating nanocapacitors due to their high ability to accumulate the charge [129]. In addition, superconducting states are also predicted for aluminene and gallenene [130,131]. Possible spheres of single-element 2D materials applications are summarized in Table 5.…”

“…Fascinating novel physical phenomena are also theoretically predicted for materials of this family that are still waiting to be experimentally discovered and investigated. Among them are various plasmonic effects and quantum Hall effect in 2D boron [91], high-temperature quantum spin Hall effect in bismuthene [83], strain-induced magnetism in aluminene [140], massless Dirac fermions, and superconductivity in gallenene [131].…”