Li_2xBC₃: a two dimensional MgB₂-like superconductor

Though most superconductors can be grouped into distinct structure classes, MgB₂ remains in a class of its own almost two decades after its discovery. Previous efforts to design superconductors in the same structure class as MgB₂ have been unsuccessful due to various complications. Recently, experimentalists are able to stabilize Li_2xBC₃ [1], a layered compound with Li sandwiched between alternating C-C and B-C honeycomb sheets similar to MgB₂. By carrying out linear response calculations, we find that at half occupation (i. e. x= 0.5), Li_2xBC3 is a phonon mediated superconductor with a T_c of around 45 K. Further increasing Li occupation (x) weakens electron-phonon coupling, thus lowering T_c. At occupation levels below 0.5, crystal structure of Li_2xBC₃ becomes dynamically unstable due to increased electron-phonon coupling. Electronic structure, Fermi surfaces and electron-phonon couplings etc of Li_2xBC3 will be presented to help understand the origin of strong electron-phonon coupling.

[1] Milashius V, Pavlyuk V, Kluziak K, Dmytriv G, Ehrenberg H. Acta Crystallogr C Struct Chem. 2017 Nov 1;73(Pt 11):984-989.