High-temperature phonon-mediated superconductivity in monolayer Mg2B4C2

Abstract

A two-dimensional material – Mg2B4C2, belonging to the family of the conventional superconductor MgB2, is theoretically predicted to exhibit superconductivity with critical temperature Tc estimated in the 47–48 K range (predicted using the McMillian-Allen-Dynes formula) without any tuning of external parameters such as doping, strain, or substrate-induced effects. The origin of such a high intrinsic Tc is ascribed to the presence of strong electron-phonon coupling and large density of states at the Fermi level. This system is obtained after replacing the chemically active boron-boron surface layers in a MgB2 slab by chemically inactive boron-carbon layers. Hence, the surfaces of this material are inert. Our calculations confirm the stability of 2D Mg2B4C2. We also find that the key features of this material remain essentially unchanged when its thickness is increased by modestly increasing the number of inner MgB2 layers.

High-Throughput DFT-Based Discovery of Next Generation Two-Dimensional (2D) Superconductors

“…Specifically, Mg 2 B 4 C 2 and W 2 N 3 have been predicted to have a T c of 47 and 21 K, respectively. 41,42 Computational predictions of superconducting transition temperatures can be most useful as a precursor to direct more expensive and time-consuming experimental synthesis and characterization. Previously, there have been several efforts to systematically discover superconducting materials which fall into certain materials classes, such as transition metals, 43 A15, B1, 44,45 AB 2 compounds, 46−48 cuprates, 49 iron-based compounds, 50 hydrides, 51−53 and many other classes of materials.…”

“…We observe the highest transition temperature for monolayer Mg 2 B 4 N 2 , which has a T c of 21.8 K. To our knowledge, this material has previously been undiscovered in bulk and 2D form. The motivation to study Mg 2 B 4 N 2 stems from the recent prediction of a high superconducting temperature (47 K) 41 for Mg 2 B 4 C 2 . In our work, we calculated the T c of 2D Mg 2 B 4 C 2 to be 9.0 K. The difference between the T c obtained in our work versus previous work can be attributed to the differences in calculation methods used (different codes, pseudopotentials, density functionals, method of perturbation theory/EPC calculation 41 ).…”

“…The motivation to study Mg 2 B 4 N 2 stems from the recent prediction of a high superconducting temperature (47 K) 41 for Mg 2 B 4 C 2 . In our work, we calculated the T c of 2D Mg 2 B 4 C 2 to be 9.0 K. The difference between the T c obtained in our work versus previous work can be attributed to the differences in calculation methods used (different codes, pseudopotentials, density functionals, method of perturbation theory/EPC calculation 41 ). Nevertheless, the substitution of carbon with nitrogen results in over a 155% increase in the superconducting transition temperature.…”

“…Using first-principles calculations, efforts have been made to screen 2D superconducting monolayers with higher T c including intrinsic 2D metals and doped 2D materials. − Two dimensional boron allotropes (such as borophene) − and carbon–boron based 2D materials such as B 2 O, B 2 C, LiBC, MgB 2 , Mo 2 C, Mg 2 B 4 C 2 , and W 2 N 3 have been predicted to have substantial critical temperatures. Specifically, Mg 2 B 4 C 2 and W 2 N 3 have been predicted to have a T c of 47 and 21 K, respectively. , Computational predictions of superconducting transition temperatures can be most useful as a precursor to direct more expensive and time-consuming experimental synthesis and characterization. Previously, there have been several efforts to systematically discover superconducting materials which fall into certain materials classes, such as transition metals, A15, B1, , AB 2 compounds, − cuprates, iron-based compounds, hydrides, − and many other classes of materials. ,− …”

“…Although this parameter can be calculated from first principles, μ* generally varies over a relatively small range (such as 0.09–0.18). Similar to several other studies involving 2D materials, ,, we take μ* = 0.1 when reporting our results from high-throughput screening.…”